Add support for time and more date formats

3 files changed, 516 insertions, 475 deletions

diff --git a/helix-core/src/increment/date.rs b/helix-core/src/increment/date.rs
deleted file mode 100644
index 05442990..00000000
--- a/helix-core/src/increment/date.rs
+++ /dev/null
@@ -1,474 +0,0 @@
-use regex::Regex;
-
-use std::borrow::Cow;
-use std::cmp;
-
-use ropey::RopeSlice;
-
-use crate::{Range, Tendril};
-
-use chrono::{Datelike, Duration, NaiveDate};
-
-use super::Increment;
-
-fn ndays_in_month(year: i32, month: u32) -> u32 {
-    // The first day of the next month...
-    let (y, m) = if month == 12 {
-        (year + 1, 1)
-    } else {
-        (year, month + 1)
-    };
-    let d = NaiveDate::from_ymd(y, m, 1);
-
-    // ...is preceded by the last day of the original month.
-    d.pred().day()
-}
-
-fn add_days(date: NaiveDate, amount: i64) -> Option<NaiveDate> {
-    date.checked_add_signed(Duration::days(amount))
-}
-
-fn add_months(date: NaiveDate, amount: i64) -> Option<NaiveDate> {
-    let month = date.month0() as i64 + amount;
-    let year = date.year() + i32::try_from(month / 12).ok()?;
-    let year = if month.is_negative() { year - 1 } else { year };
-
-    // Normalize month
-    let month = month % 12;
-    let month = if month.is_negative() {
-        month + 13
-    } else {
-        month + 1
-    } as u32;
-
-    let day = cmp::min(date.day(), ndays_in_month(year, month));
-
-    Some(NaiveDate::from_ymd(year, month, day))
-}
-
-fn add_years(date: NaiveDate, amount: i64) -> Option<NaiveDate> {
-    let year = i32::try_from(date.year() as i64 + amount).ok()?;
-    let ndays = ndays_in_month(year, date.month());
-
-    if date.day() > ndays {
-        let d = NaiveDate::from_ymd(year, date.month(), ndays);
-        Some(d.succ())
-    } else {
-        date.with_year(year)
-    }
-}
-
-#[derive(Copy, Clone, Debug, PartialEq, Eq)]
-struct Format {
-    regex: &'static str,
-    separator: char,
-}
-
-// Only support formats that aren't region specific.
-static FORMATS: &[Format] = &[
-    Format {
-        regex: r"(\d{4})-(\d{2})-(\d{2})",
-        separator: '-',
-    },
-    Format {
-        regex: r"(\d{4})/(\d{2})/(\d{2})",
-        separator: '/',
-    },
-];
-
-const DATE_LENGTH: usize = 10;
-
-#[derive(Copy, Clone, Debug, PartialEq, Eq)]
-enum DateField {
-    Year,
-    Month,
-    Day,
-}
-
-#[derive(Debug, PartialEq, Eq)]
-pub struct DateIncrementor {
-    date: NaiveDate,
-    range: Range,
-    field: DateField,
-    format: Format,
-}
-
-impl DateIncrementor {
-    pub fn from_range(text: RopeSlice, range: Range) -> Option<DateIncrementor> {
-        let range = if range.is_empty() {
-            if range.anchor < text.len_bytes() {
-                // Treat empty range as a cursor range.
-                range.put_cursor(text, range.anchor + 1, true)
-            } else {
-                // The range is empty and at the end of the text.
-                return None;
-            }
-        } else {
-            range
-        };
-
-        let from = range.from().saturating_sub(DATE_LENGTH);
-        let to = (range.from() + DATE_LENGTH).min(text.len_chars());
-
-        let (from_in_text, to_in_text) = (range.from() - from, range.to() - from);
-        let text: Cow<str> = text.slice(from..to).into();
-
-        FORMATS.iter().find_map(|&format| {
-            let re = Regex::new(format.regex).ok()?;
-            let captures = re.captures(&text)?;
-
-            let date = captures.get(0)?;
-            let offset = range.from() - from_in_text;
-            let range = Range::new(date.start() + offset, date.end() + offset);
-
-            let (year, month, day) = (captures.get(1)?, captures.get(2)?, captures.get(3)?);
-            let (year_range, month_range, day_range) = (year.range(), month.range(), day.range());
-
-            let field = if year_range.contains(&from_in_text)
-                && year_range.contains(&(to_in_text - 1))
-            {
-                DateField::Year
-            } else if month_range.contains(&from_in_text) && month_range.contains(&(to_in_text - 1))
-            {
-                DateField::Month
-            } else if day_range.contains(&from_in_text) && day_range.contains(&(to_in_text - 1)) {
-                DateField::Day
-            } else {
-                return None;
-            };
-
-            let date = NaiveDate::from_ymd_opt(
-                year.as_str().parse::<i32>().ok()?,
-                month.as_str().parse::<u32>().ok()?,
-                day.as_str().parse::<u32>().ok()?,
-            )?;
-
-            Some(DateIncrementor {
-                date,
-                field,
-                range,
-                format,
-            })
-        })
-    }
-}
-
-impl Increment for DateIncrementor {
-    fn increment(&self, amount: i64) -> (Range, Tendril) {
-        let date = match self.field {
-            DateField::Year => add_years(self.date, amount),
-            DateField::Month => add_months(self.date, amount),
-            DateField::Day => add_days(self.date, amount),
-        }
-        .unwrap_or(self.date);
-
-        (
-            self.range,
-            format!(
-                "{:04}{}{:02}{}{:02}",
-                date.year(),
-                self.format.separator,
-                date.month(),
-                self.format.separator,
-                date.day()
-            )
-            .into(),
-        )
-    }
-}
-
-#[cfg(test)]
-mod test {
-    use super::*;
-    use crate::Rope;
-
-    #[test]
-    fn test_create_incrementor_for_year_with_dashes() {
-        let rope = Rope::from_str("2021-11-15");
-
-        for cursor in 0..=3 {
-            let range = Range::new(cursor, cursor + 1);
-            assert_eq!(
-                DateIncrementor::from_range(rope.slice(..), range),
-                Some(DateIncrementor {
-                    date: NaiveDate::from_ymd(2021, 11, 15),
-                    range: Range::new(0, 10),
-                    field: DateField::Year,
-                    format: FORMATS[0],
-                })
-            );
-        }
-    }
-
-    #[test]
-    fn test_create_incrementor_for_month_with_dashes() {
-        let rope = Rope::from_str("2021-11-15");
-
-        for cursor in 5..=6 {
-            let range = Range::new(cursor, cursor + 1);
-            assert_eq!(
-                DateIncrementor::from_range(rope.slice(..), range),
-                Some(DateIncrementor {
-                    date: NaiveDate::from_ymd(2021, 11, 15),
-                    range: Range::new(0, 10),
-                    field: DateField::Month,
-                    format: FORMATS[0],
-                })
-            );
-        }
-    }
-
-    #[test]
-    fn test_create_incrementor_for_day_with_dashes() {
-        let rope = Rope::from_str("2021-11-15");
-
-        for cursor in 8..=9 {
-            let range = Range::new(cursor, cursor + 1);
-            assert_eq!(
-                DateIncrementor::from_range(rope.slice(..), range),
-                Some(DateIncrementor {
-                    date: NaiveDate::from_ymd(2021, 11, 15),
-                    range: Range::new(0, 10),
-                    field: DateField::Day,
-                    format: FORMATS[0],
-                })
-            );
-        }
-    }
-
-    #[test]
-    fn test_try_create_incrementor_on_dashes() {
-        let rope = Rope::from_str("2021-11-15");
-
-        for &cursor in &[4, 7] {
-            let range = Range::new(cursor, cursor + 1);
-            assert_eq!(DateIncrementor::from_range(rope.slice(..), range), None,);
-        }
-    }
-
-    #[test]
-    fn test_create_incrementor_for_year_with_slashes() {
-        let rope = Rope::from_str("2021/11/15");
-
-        for cursor in 0..=3 {
-            let range = Range::new(cursor, cursor + 1);
-            assert_eq!(
-                DateIncrementor::from_range(rope.slice(..), range),
-                Some(DateIncrementor {
-                    date: NaiveDate::from_ymd(2021, 11, 15),
-                    range: Range::new(0, 10),
-                    field: DateField::Year,
-                    format: FORMATS[1],
-                })
-            );
-        }
-    }
-
-    #[test]
-    fn test_create_incrementor_for_month_with_slashes() {
-        let rope = Rope::from_str("2021/11/15");
-
-        for cursor in 5..=6 {
-            let range = Range::new(cursor, cursor + 1);
-            assert_eq!(
-                DateIncrementor::from_range(rope.slice(..), range),
-                Some(DateIncrementor {
-                    date: NaiveDate::from_ymd(2021, 11, 15),
-                    range: Range::new(0, 10),
-                    field: DateField::Month,
-                    format: FORMATS[1],
-                })
-            );
-        }
-    }
-
-    #[test]
-    fn test_create_incrementor_for_day_with_slashes() {
-        let rope = Rope::from_str("2021/11/15");
-
-        for cursor in 8..=9 {
-            let range = Range::new(cursor, cursor + 1);
-            assert_eq!(
-                DateIncrementor::from_range(rope.slice(..), range),
-                Some(DateIncrementor {
-                    date: NaiveDate::from_ymd(2021, 11, 15),
-                    range: Range::new(0, 10),
-                    field: DateField::Day,
-                    format: FORMATS[1],
-                })
-            );
-        }
-    }
-
-    #[test]
-    fn test_try_create_incrementor_on_slashes() {
-        let rope = Rope::from_str("2021/11/15");
-
-        for &cursor in &[4, 7] {
-            let range = Range::new(cursor, cursor + 1);
-            assert_eq!(DateIncrementor::from_range(rope.slice(..), range), None,);
-        }
-    }
-
-    #[test]
-    fn test_date_surrounded_by_spaces() {
-        let rope = Rope::from_str("   2021-11-15  ");
-        let range = Range::new(3, 4);
-        assert_eq!(
-            DateIncrementor::from_range(rope.slice(..), range),
-            Some(DateIncrementor {
-                date: NaiveDate::from_ymd(2021, 11, 15),
-                range: Range::new(3, 13),
-                field: DateField::Year,
-                format: FORMATS[0],
-            })
-        );
-    }
-
-    #[test]
-    fn test_date_in_single_quotes() {
-        let rope = Rope::from_str("date = '2021-11-15'");
-        let range = Range::new(10, 11);
-        assert_eq!(
-            DateIncrementor::from_range(rope.slice(..), range),
-            Some(DateIncrementor {
-                date: NaiveDate::from_ymd(2021, 11, 15),
-                range: Range::new(8, 18),
-                field: DateField::Year,
-                format: FORMATS[0],
-            })
-        );
-    }
-
-    #[test]
-    fn test_date_in_double_quotes() {
-        let rope = Rope::from_str("let date = \"2021-11-15\";");
-        let range = Range::new(12, 13);
-        assert_eq!(
-            DateIncrementor::from_range(rope.slice(..), range),
-            Some(DateIncrementor {
-                date: NaiveDate::from_ymd(2021, 11, 15),
-                range: Range::new(12, 22),
-                field: DateField::Year,
-                format: FORMATS[0],
-            })
-        );
-    }
-
-    #[test]
-    fn test_date_cursor_one_right_of_date() {
-        let rope = Rope::from_str("2021-11-15 ");
-        let range = Range::new(10, 11);
-        assert_eq!(DateIncrementor::from_range(rope.slice(..), range), None);
-    }
-
-    #[test]
-    fn test_date_cursor_one_left_of_number() {
-        let rope = Rope::from_str(" 2021-11-15");
-        let range = Range::new(0, 1);
-        assert_eq!(DateIncrementor::from_range(rope.slice(..), range), None);
-    }
-
-    #[test]
-    fn test_date_empty_range_at_beginning() {
-        let rope = Rope::from_str("2021-11-15");
-        let range = Range::point(0);
-        assert_eq!(
-            DateIncrementor::from_range(rope.slice(..), range),
-            Some(DateIncrementor {
-                date: NaiveDate::from_ymd(2021, 11, 15),
-                range: Range::new(0, 10),
-                field: DateField::Year,
-                format: FORMATS[0],
-            })
-        );
-    }
-
-    #[test]
-    fn test_date_empty_range_at_in_middle() {
-        let rope = Rope::from_str("2021-11-15");
-        let range = Range::point(5);
-        assert_eq!(
-            DateIncrementor::from_range(rope.slice(..), range),
-            Some(DateIncrementor {
-                date: NaiveDate::from_ymd(2021, 11, 15),
-                range: Range::new(0, 10),
-                field: DateField::Month,
-                format: FORMATS[0],
-            })
-        );
-    }
-
-    #[test]
-    fn test_date_empty_range_at_end() {
-        let rope = Rope::from_str("2021-11-15");
-        let range = Range::point(10);
-        assert_eq!(DateIncrementor::from_range(rope.slice(..), range), None);
-    }
-
-    #[test]
-    fn test_invalid_dates() {
-        let tests = [
-            "0000-00-00",
-            "1980-2-21",
-            "1980-12-1",
-            "12345",
-            "2020-02-30",
-            "1999-12-32",
-            "19-12-32",
-            "1-2-3",
-            "0000/00/00",
-            "1980/2/21",
-            "1980/12/1",
-            "12345",
-            "2020/02/30",
-            "1999/12/32",
-            "19/12/32",
-            "1/2/3",
-        ];
-
-        for invalid in tests {
-            let rope = Rope::from_str(invalid);
-            let range = Range::new(0, 1);
-
-            assert_eq!(DateIncrementor::from_range(rope.slice(..), range), None);
-        }
-    }
-
-    #[test]
-    fn test_increment_dates() {
-        let tests = [
-            // (original, cursor, amount, expected)
-            ("2020-02-28", 0, 1, "2021-02-28"),
-            ("2020-02-29", 0, 1, "2021-03-01"),
-            ("2020-01-31", 5, 1, "2020-02-29"),
-            ("2020-01-20", 5, 1, "2020-02-20"),
-            ("2021-01-01", 5, -1, "2020-12-01"),
-            ("2021-01-31", 5, -2, "2020-11-30"),
-            ("2020-02-28", 8, 1, "2020-02-29"),
-            ("2021-02-28", 8, 1, "2021-03-01"),
-            ("2021-02-28", 0, -1, "2020-02-28"),
-            ("2021-03-01", 0, -1, "2020-03-01"),
-            ("2020-02-29", 5, -1, "2020-01-29"),
-            ("2020-02-20", 5, -1, "2020-01-20"),
-            ("2020-02-29", 8, -1, "2020-02-28"),
-            ("2021-03-01", 8, -1, "2021-02-28"),
-            ("1980/12/21", 8, 100, "1981/03/31"),
-            ("1980/12/21", 8, -100, "1980/09/12"),
-            ("1980/12/21", 8, 1000, "1983/09/17"),
-            ("1980/12/21", 8, -1000, "1978/03/27"),
-        ];
-
-        for (original, cursor, amount, expected) in tests {
-            let rope = Rope::from_str(original);
-            let range = Range::new(cursor, cursor + 1);
-            assert_eq!(
-                DateIncrementor::from_range(rope.slice(..), range)
-                    .unwrap()
-                    .increment(amount)
-                    .1,
-                expected.into()
-            );
-        }
-    }
-}
diff --git a/helix-core/src/increment/date_time.rs b/helix-core/src/increment/date_time.rs
new file mode 100644
index 00000000..39380104
--- /dev/null
+++ b/helix-core/src/increment/date_time.rs
@@ -0,0 +1,515 @@
+use chrono::{Datelike, Duration, NaiveDate, NaiveDateTime, NaiveTime, Timelike};
+use once_cell::sync::Lazy;
+use regex::Regex;
+use ropey::RopeSlice;
+
+use std::borrow::Cow;
+use std::cmp;
+
+use super::Increment;
+use crate::{Range, Tendril};
+
+#[derive(Debug, PartialEq, Eq)]
+pub struct DateTimeIncrementor {
+    date_time: NaiveDateTime,
+    range: Range,
+    format: Format,
+    field: DateField,
+}
+
+impl DateTimeIncrementor {
+    pub fn from_range(text: RopeSlice, range: Range) -> Option<DateTimeIncrementor> {
+        let range = if range.is_empty() {
+            if range.anchor < text.len_chars() {
+                // Treat empty range as a cursor range.
+                range.put_cursor(text, range.anchor + 1, true)
+            } else {
+                // The range is empty and at the end of the text.
+                return None;
+            }
+        } else {
+            range
+        };
+
+        FORMATS.iter().find_map(|format| {
+            let from = range.from().saturating_sub(format.max_len);
+            let to = (range.from() + format.max_len).min(text.len_chars());
+
+            let (from_in_text, to_in_text) = (range.from() - from, range.to() - from);
+            let text: Cow<str> = text.slice(from..to).into();
+
+            let captures = format.regex.captures(&text)?;
+            if captures.len() - 1 != format.fields.len() {
+                return None;
+            }
+
+            let date_time = captures.get(0)?;
+            let offset = range.from() - from_in_text;
+            let range = Range::new(date_time.start() + offset, date_time.end() + offset);
+
+            let field = captures
+                .iter()
+                .skip(1)
+                .enumerate()
+                .find_map(|(i, capture)| {
+                    let capture = capture?;
+                    let capture_range = capture.range();
+
+                    if capture_range.contains(&from_in_text)
+                        && capture_range.contains(&(to_in_text - 1))
+                    {
+                        Some(format.fields[i])
+                    } else {
+                        None
+                    }
+                })?;
+
+            let has_date = format.fields.iter().any(|f| f.unit.is_date());
+            let has_time = format.fields.iter().any(|f| f.unit.is_time());
+
+            let date_time = match (has_date, has_time) {
+                (true, true) => NaiveDateTime::parse_from_str(
+                    &text[date_time.start()..date_time.end()],
+                    format.fmt,
+                )
+                .ok()?,
+                (true, false) => {
+                    let date = NaiveDate::parse_from_str(
+                        &text[date_time.start()..date_time.end()],
+                        format.fmt,
+                    )
+                    .ok()?;
+
+                    date.and_hms(0, 0, 0)
+                }
+                (false, true) => {
+                    let time = NaiveTime::parse_from_str(
+                        &text[date_time.start()..date_time.end()],
+                        format.fmt,
+                    )
+                    .ok()?;
+
+                    NaiveDate::from_ymd(0, 1, 1).and_time(time)
+                }
+                (false, false) => return None,
+            };
+
+            Some(DateTimeIncrementor {
+                date_time,
+                range,
+                format: format.clone(),
+                field,
+            })
+        })
+    }
+}
+
+impl Increment for DateTimeIncrementor {
+    fn increment(&self, amount: i64) -> (Range, Tendril) {
+        let date_time = match self.field.unit {
+            DateUnit::Years => add_years(self.date_time, amount),
+            DateUnit::Months => add_months(self.date_time, amount),
+            DateUnit::Days => add_duration(self.date_time, Duration::days(amount)),
+            DateUnit::Hours => add_duration(self.date_time, Duration::hours(amount)),
+            DateUnit::Minutes => add_duration(self.date_time, Duration::minutes(amount)),
+            DateUnit::Seconds => add_duration(self.date_time, Duration::seconds(amount)),
+            DateUnit::AmPm => toggle_am_pm(self.date_time),
+        }
+        .unwrap_or(self.date_time);
+
+        (
+            self.range,
+            date_time.format(self.format.fmt).to_string().into(),
+        )
+    }
+}
+
+static FORMATS: Lazy<Vec<Format>> = Lazy::new(|| {
+    vec![
+        Format::new("%Y-%m-%d %H:%M:%S"), // 2021-11-24 07:12:23
+        Format::new("%Y/%m/%d %H:%M:%S"), // 2021/11/24 07:12:23
+        Format::new("%Y-%m-%d %H:%M"),    // 2021-11-24 07:12
+        Format::new("%Y/%m/%d %H:%M"),    // 2021/11/24 07:12
+        Format::new("%Y-%m-%d"),          // 2021-11-24
+        Format::new("%Y/%m/%d"),          // 2021/11/24
+        Format::new("%a %b %d %Y"),       // Wed Nov 24 2021
+        Format::new("%d-%b-%Y"),          // 24-Nov-2021
+        Format::new("%Y %b %d"),          // 2021 Nov 24
+        Format::new("%b %d, %Y"),         // Nov 24, 2021
+        Format::new("%-I:%M:%S %P"),      // 7:21:53 am
+        Format::new("%-I:%M %P"),         // 7:21 am
+        Format::new("%-I:%M:%S %p"),      // 7:21:53 AM
+        Format::new("%-I:%M %p"),         // 7:21 AM
+        Format::new("%H:%M:%S"),          // 23:24:23
+        Format::new("%H:%M"),             // 23:24
+    ]
+});
+
+#[derive(Clone, Debug)]
+struct Format {
+    fmt: &'static str,
+    fields: Vec<DateField>,
+    regex: Regex,
+    max_len: usize,
+}
+
+impl Format {
+    fn new(fmt: &'static str) -> Self {
+        let mut remaining = fmt;
+        let mut fields = Vec::new();
+        let mut regex = String::new();
+        let mut max_len = 0;
+
+        while let Some(i) = remaining.find('%') {
+            let mut chars = remaining[i + 1..].chars();
+            let spec_len = if let Some(c) = chars.next() {
+                if c == '-' {
+                    if chars.next().is_some() {
+                        2
+                    } else {
+                        0
+                    }
+                } else {
+                    1
+                }
+            } else {
+                0
+            };
+
+            if i < remaining.len() - spec_len {
+                let specifier = &remaining[i + 1..i + 1 + spec_len];
+                if let Some(field) = DateField::from_specifier(specifier) {
+                    fields.push(field);
+                    max_len += field.max_len + remaining[..i].len();
+                    regex += &remaining[..i];
+                    regex += &format!("({})", field.regex);
+                    remaining = &remaining[i + spec_len + 1..];
+                } else {
+                    regex += &remaining[..=i];
+                }
+            } else {
+                regex += remaining;
+            }
+        }
+
+        let regex = Regex::new(&regex).unwrap();
+
+        Self {
+            fmt,
+            fields,
+            regex,
+            max_len,
+        }
+    }
+}
+
+impl PartialEq for Format {
+    fn eq(&self, other: &Self) -> bool {
+        self.fmt == other.fmt && self.fields == other.fields && self.max_len == other.max_len
+    }
+}
+
+impl Eq for Format {}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+struct DateField {
+    regex: &'static str,
+    unit: DateUnit,
+    max_len: usize,
+}
+
+impl DateField {
+    fn from_specifier(specifier: &str) -> Option<Self> {
+        match specifier {
+            "Y" => Some(DateField {
+                regex: r"\d{4}",
+                unit: DateUnit::Years,
+                max_len: 5,
+            }),
+            "y" => Some(DateField {
+                regex: r"\d\d",
+                unit: DateUnit::Years,
+                max_len: 2,
+            }),
+            "m" => Some(DateField {
+                regex: r"[0-1]\d",
+                unit: DateUnit::Months,
+                max_len: 2,
+            }),
+            "d" => Some(DateField {
+                regex: r"[0-3]\d",
+                unit: DateUnit::Days,
+                max_len: 2,
+            }),
+            "-d" => Some(DateField {
+                regex: r"[1-3]?\d",
+                unit: DateUnit::Days,
+                max_len: 2,
+            }),
+            "a" => Some(DateField {
+                regex: r"Sun|Mon|Tue|Wed|Thu|Fri|Sat",
+                unit: DateUnit::Days,
+                max_len: 3,
+            }),
+            "A" => Some(DateField {
+                regex: r"Sunday|Monday|Tuesday|Wednesday|Thursday|Friday|Saturday",
+                unit: DateUnit::Days,
+                max_len: 9,
+            }),
+            "b" | "h" => Some(DateField {
+                regex: r"Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec",
+                unit: DateUnit::Months,
+                max_len: 3,
+            }),
+            "B" => Some(DateField {
+                regex: r"January|February|March|April|May|June|July|August|September|October|November|December",
+                unit: DateUnit::Months,
+                max_len: 9,
+            }),
+            "H" => Some(DateField {
+                regex: r"[0-2]\d",
+                unit: DateUnit::Hours,
+                max_len: 2,
+            }),
+            "M" => Some(DateField {
+                regex: r"[0-5]\d",
+                unit: DateUnit::Minutes,
+                max_len: 2,
+            }),
+            "S" => Some(DateField {
+                regex: r"[0-5]\d",
+                unit: DateUnit::Seconds,
+                max_len: 2,
+            }),
+            "I" => Some(DateField {
+                regex: r"[0-1]\d",
+                unit: DateUnit::Hours,
+                max_len: 2,
+            }),
+            "-I" => Some(DateField {
+                regex: r"1?\d",
+                unit: DateUnit::Hours,
+                max_len: 2,
+            }),
+            "P" => Some(DateField {
+                regex: r"am|pm",
+                unit: DateUnit::AmPm,
+                max_len: 2,
+            }),
+            "p" => Some(DateField {
+                regex: r"AM|PM",
+                unit: DateUnit::AmPm,
+                max_len: 2,
+            }),
+            _ => None,
+        }
+    }
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+enum DateUnit {
+    Years,
+    Months,
+    Days,
+    Hours,
+    Minutes,
+    Seconds,
+    AmPm,
+}
+
+impl DateUnit {
+    fn is_date(self) -> bool {
+        matches!(self, DateUnit::Years | DateUnit::Months | DateUnit::Days)
+    }
+
+    fn is_time(self) -> bool {
+        matches!(
+            self,
+            DateUnit::Hours | DateUnit::Minutes | DateUnit::Seconds
+        )
+    }
+}
+
+fn ndays_in_month(year: i32, month: u32) -> u32 {
+    // The first day of the next month...
+    let (y, m) = if month == 12 {
+        (year + 1, 1)
+    } else {
+        (year, month + 1)
+    };
+    let d = NaiveDate::from_ymd(y, m, 1);
+
+    // ...is preceded by the last day of the original month.
+    d.pred().day()
+}
+
+fn add_months(date_time: NaiveDateTime, amount: i64) -> Option<NaiveDateTime> {
+    let month = date_time.month0() as i64 + amount;
+    let year = date_time.year() + i32::try_from(month / 12).ok()?;
+    let year = if month.is_negative() { year - 1 } else { year };
+
+    // Normalize month
+    let month = month % 12;
+    let month = if month.is_negative() {
+        month + 13
+    } else {
+        month + 1
+    } as u32;
+
+    let day = cmp::min(date_time.day(), ndays_in_month(year, month));
+
+    Some(NaiveDate::from_ymd(year, month, day).and_time(date_time.time()))
+}
+
+fn add_years(date_time: NaiveDateTime, amount: i64) -> Option<NaiveDateTime> {
+    let year = i32::try_from(date_time.year() as i64 + amount).ok()?;
+    let ndays = ndays_in_month(year, date_time.month());
+
+    if date_time.day() > ndays {
+        let d = NaiveDate::from_ymd(year, date_time.month(), ndays);
+        Some(d.succ().and_time(date_time.time()))
+    } else {
+        date_time.with_year(year)
+    }
+}
+
+fn add_duration(date_time: NaiveDateTime, duration: Duration) -> Option<NaiveDateTime> {
+    date_time.checked_add_signed(duration)
+}
+
+fn toggle_am_pm(date_time: NaiveDateTime) -> Option<NaiveDateTime> {
+    if date_time.hour() < 12 {
+        add_duration(date_time, Duration::hours(12))
+    } else {
+        add_duration(date_time, Duration::hours(-12))
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::Rope;
+
+    #[test]
+    fn test_increment_date_times() {
+        let tests = [
+            // (original, cursor, amount, expected)
+            ("2020-02-28", 0, 1, "2021-02-28"),
+            ("2020-02-29", 0, 1, "2021-03-01"),
+            ("2020-01-31", 5, 1, "2020-02-29"),
+            ("2020-01-20", 5, 1, "2020-02-20"),
+            ("2021-01-01", 5, -1, "2020-12-01"),
+            ("2021-01-31", 5, -2, "2020-11-30"),
+            ("2020-02-28", 8, 1, "2020-02-29"),
+            ("2021-02-28", 8, 1, "2021-03-01"),
+            ("2021-02-28", 0, -1, "2020-02-28"),
+            ("2021-03-01", 0, -1, "2020-03-01"),
+            ("2020-02-29", 5, -1, "2020-01-29"),
+            ("2020-02-20", 5, -1, "2020-01-20"),
+            ("2020-02-29", 8, -1, "2020-02-28"),
+            ("2021-03-01", 8, -1, "2021-02-28"),
+            ("1980/12/21", 8, 100, "1981/03/31"),
+            ("1980/12/21", 8, -100, "1980/09/12"),
+            ("1980/12/21", 8, 1000, "1983/09/17"),
+            ("1980/12/21", 8, -1000, "1978/03/27"),
+            ("2021-11-24 07:12:23", 0, 1, "2022-11-24 07:12:23"),
+            ("2021-11-24 07:12:23", 5, 1, "2021-12-24 07:12:23"),
+            ("2021-11-24 07:12:23", 8, 1, "2021-11-25 07:12:23"),
+            ("2021-11-24 07:12:23", 11, 1, "2021-11-24 08:12:23"),
+            ("2021-11-24 07:12:23", 14, 1, "2021-11-24 07:13:23"),
+            ("2021-11-24 07:12:23", 17, 1, "2021-11-24 07:12:24"),
+            ("2021/11/24 07:12:23", 0, 1, "2022/11/24 07:12:23"),
+            ("2021/11/24 07:12:23", 5, 1, "2021/12/24 07:12:23"),
+            ("2021/11/24 07:12:23", 8, 1, "2021/11/25 07:12:23"),
+            ("2021/11/24 07:12:23", 11, 1, "2021/11/24 08:12:23"),
+            ("2021/11/24 07:12:23", 14, 1, "2021/11/24 07:13:23"),
+            ("2021/11/24 07:12:23", 17, 1, "2021/11/24 07:12:24"),
+            ("2021-11-24 07:12", 0, 1, "2022-11-24 07:12"),
+            ("2021-11-24 07:12", 5, 1, "2021-12-24 07:12"),
+            ("2021-11-24 07:12", 8, 1, "2021-11-25 07:12"),
+            ("2021-11-24 07:12", 11, 1, "2021-11-24 08:12"),
+            ("2021-11-24 07:12", 14, 1, "2021-11-24 07:13"),
+            ("2021/11/24 07:12", 0, 1, "2022/11/24 07:12"),
+            ("2021/11/24 07:12", 5, 1, "2021/12/24 07:12"),
+            ("2021/11/24 07:12", 8, 1, "2021/11/25 07:12"),
+            ("2021/11/24 07:12", 11, 1, "2021/11/24 08:12"),
+            ("2021/11/24 07:12", 14, 1, "2021/11/24 07:13"),
+            ("Wed Nov 24 2021", 0, 1, "Thu Nov 25 2021"),
+            ("Wed Nov 24 2021", 4, 1, "Fri Dec 24 2021"),
+            ("Wed Nov 24 2021", 8, 1, "Thu Nov 25 2021"),
+            ("Wed Nov 24 2021", 11, 1, "Thu Nov 24 2022"),
+            ("24-Nov-2021", 0, 1, "25-Nov-2021"),
+            ("24-Nov-2021", 3, 1, "24-Dec-2021"),
+            ("24-Nov-2021", 7, 1, "24-Nov-2022"),
+            ("2021 Nov 24", 0, 1, "2022 Nov 24"),
+            ("2021 Nov 24", 5, 1, "2021 Dec 24"),
+            ("2021 Nov 24", 9, 1, "2021 Nov 25"),
+            ("Nov 24, 2021", 0, 1, "Dec 24, 2021"),
+            ("Nov 24, 2021", 4, 1, "Nov 25, 2021"),
+            ("Nov 24, 2021", 8, 1, "Nov 24, 2022"),
+            ("7:21:53 am", 0, 1, "8:21:53 am"),
+            ("7:21:53 am", 3, 1, "7:22:53 am"),
+            ("7:21:53 am", 5, 1, "7:21:54 am"),
+            ("7:21:53 am", 8, 1, "7:21:53 pm"),
+            ("7:21:53 AM", 0, 1, "8:21:53 AM"),
+            ("7:21:53 AM", 3, 1, "7:22:53 AM"),
+            ("7:21:53 AM", 5, 1, "7:21:54 AM"),
+            ("7:21:53 AM", 8, 1, "7:21:53 PM"),
+            ("7:21 am", 0, 1, "8:21 am"),
+            ("7:21 am", 3, 1, "7:22 am"),
+            ("7:21 am", 5, 1, "7:21 pm"),
+            ("7:21 AM", 0, 1, "8:21 AM"),
+            ("7:21 AM", 3, 1, "7:22 AM"),
+            ("7:21 AM", 5, 1, "7:21 PM"),
+            ("23:24:23", 1, 1, "00:24:23"),
+            ("23:24:23", 3, 1, "23:25:23"),
+            ("23:24:23", 6, 1, "23:24:24"),
+            ("23:24", 1, 1, "00:24"),
+            ("23:24", 3, 1, "23:25"),
+        ];
+
+        for (original, cursor, amount, expected) in tests {
+            let rope = Rope::from_str(original);
+            let range = Range::new(cursor, cursor + 1);
+            assert_eq!(
+                DateTimeIncrementor::from_range(rope.slice(..), range)
+                    .unwrap()
+                    .increment(amount)
+                    .1,
+                expected.into()
+            );
+        }
+    }
+
+    #[test]
+    fn test_invalid_date_times() {
+        let tests = [
+            "0000-00-00",
+            "1980-2-21",
+            "1980-12-1",
+            "12345",
+            "2020-02-30",
+            "1999-12-32",
+            "19-12-32",
+            "1-2-3",
+            "0000/00/00",
+            "1980/2/21",
+            "1980/12/1",
+            "12345",
+            "2020/02/30",
+            "1999/12/32",
+            "19/12/32",
+            "1/2/3",
+            "123:456:789",
+            "11:61",
+            "2021-55-12 08:12:54",
+        ];
+
+        for invalid in tests {
+            let rope = Rope::from_str(invalid);
+            let range = Range::new(0, 1);
+
+            assert_eq!(DateTimeIncrementor::from_range(rope.slice(..), range), None)
+        }
+    }
+}
diff --git a/helix-core/src/increment/mod.rs b/helix-core/src/increment/mod.rs
index 71a1f183..f5945774 100644
--- a/helix-core/src/increment/mod.rs
+++ b/helix-core/src/increment/mod.rs
@@ -1,4 +1,4 @@
-pub mod date;
+pub mod date_time;
 pub mod number;
 
 use crate::{Range, Tendril};