ADD datetime calculation

Co-authored-by: LordBaryhobal <lordbaryhobal@gmail.com>

src/datetime_calc.typ

@@ -0,0 +1,242 @@
+#let is-leap-year(year) = {
+  if calc.rem(year, 4) != 0 {
+    return false
+  }
+  if calc.rem(year, 100) != 0 {
+    return true
+  }
+  return calc.rem(year, 400) == 0
+}
+
+#let get-month-days(month, year) = {
+  let leap = is-leap-year(year)
+  
+  if month == 2 {
+    return if leap {29} else {28}
+  }
+
+  if month >= 8 {
+    month += 1
+  }
+  return if calc.rem(month, 2) == 0 {30} else {31}
+}
+
+#let add(dt, days) = {
+  assert(days >= 0, message: "days cannot be negative; use sub()")
+  
+  let day = dt.day()
+  let month = dt.month()
+  let year = dt.year()
+  let month-days = get-month-days(month, year)
+  let leap = is-leap-year(year)
+
+  for _ in range(days) {
+    if day == month-days {
+      month += 1
+      day = 1
+      if month == 13 {
+        year += 1
+        month = 1
+        leap = is-leap-year(year)
+      }
+      month-days = get-month-days(month, year)
+    } else {
+      day += 1
+    }
+  }
+  return datetime(day: day, month: month, year: year)
+}
+
+#let sub(dt, days) = {
+  assert(days >= 0, message: "days cannot be negative; use add()")
+  
+  let day = dt.day()
+  let month = dt.month()
+  let year = dt.year()
+  let month-days = get-month-days(month, year)
+  let leap = is-leap-year(year)
+
+  for _ in range(days) {
+    if day == 1 {
+      month -= 1
+      if month == 0 {
+        year -= 1
+        month = 12
+        leap = is-leap-year(year)
+      }
+      month-days = get-month-days(month, year)
+      day = month-days
+    } else {
+      day -= 1
+    }
+  }
+  return datetime(day: day, month: month, year: year)
+}
+
+#let offset(dt, days) = {
+  if days < 0 {
+    return sub(dt, -days)
+  }
+  return add(dt, days)
+}
+
+#let add-week-workingdays(dt, weeks) = {
+  let int_part = int(weeks)
+  let float_part = int( (weeks - int_part)*5 + 0.01 )
+  let new_date = add(dt, int_part*7)
+
+  let i = 0
+  while i < float_part {
+    new_date = add(new_date, 1)
+    if new_date.weekday() == 6 {
+      new_date = add(new_date, 2)
+    }
+    if new_date.weekday() == 7 {
+      new_date = add(new_date, 1)
+    }
+    i += 1
+  }
+  return new_date
+}
+
+#let diff-days(a, b) = {
+  let days = 0
+  let neg = b < a
+  if neg {
+    let c = a
+    a = b
+    b = c
+  }
+  while (a < b) {
+    days += 1
+    a = add(a, 1)
+  }
+  return if neg {-days} else {days}
+}
+#let diff-weeks(start_date, finish_date) = {
+  calc.round(
+    diff-days(
+      start_date,
+      add(finish_date, 1)
+    )/7,
+    digits: 2
+  )
+}
+#let diff-weeks-workingday(start_date, finish_date) = {
+  let days = 0
+  while (start_date <= finish_date) {
+    if start_date.weekday() != 6 and start_date.weekday() != 7 {
+      days += 1
+    }
+    start_date = add(start_date, 1)
+  }
+  return days/5
+}
+#let diff-months(start_date, finish_date) = {
+  calc.round(
+    diff-days(
+      start_date,
+      add(finish_date, 1)
+    )/30,
+    digits: 2
+  )
+}
+
+#let count-weeks(a, b) = {
+  let weeks = 0
+  let neg = b < a
+  if neg {
+    let c = a
+    a = b
+    b = c
+  }
+  while (a < b) {
+    weeks += 1
+    a = add(a, 7)
+  }
+  return if neg {-weeks} else {weeks}
+}
+#let count-months(a, b) = {
+  let months = 0
+  let neg = b < a
+  if neg {
+    let c = a
+    a = b
+    b = c
+  }
+  while (a < b) {
+    months += 1
+    a = add(a, 30)
+  }
+  return if neg {-months} else {months}
+}
+
+#let count-years(a, b) = {
+  let years = 0
+  let neg = b < a
+  if neg {
+    let c = a
+    a = b
+    b = c
+  }
+  while (a < b) {
+    years += 1
+    a = add(a, 365)
+  }
+  return if neg {-years} else {years}
+}
+
+#let remaining_week_on_month(date) ={
+  diff-weeks(
+    date,
+    datetime(
+      year: date.year(),
+      month: date.month(),
+      day: get-month-days(date.month(), date.year())
+    )
+  )
+}
+
+#let remaining_week_on_month-workingday(date) ={
+  diff-weeks-workingday(
+    date,
+    datetime(
+      year: date.year(),
+      month: date.month(),
+      day: get-month-days(date.month(), date.year())
+    )
+  )
+}
+
+#let remaining_week_on_year(date) ={
+  diff-weeks(
+    date,
+    datetime(
+      year: date.year(),
+      month: 12,
+      day: 31
+    )
+  )
+}
+
+#let workingday_ratio(date) = {
+  let weekday = date.weekday() -1
+  if weekday == 6 {
+    weekday = 5
+  }
+  if weekday == 7 {
+    weekday = 5
+  }
+  return weekday/5
+}
+
+
+#let equalDate(date1, date2) = {
+  let year = date1.year() == date2.year()
+  let month = date1.month() == date2.month()
+  let day = date1.day() == date2.day()
+
+  return year and month and day
+}
+
+