Relative DateTime modifiers

[pmdevita]

One feature that I would find useful built into the library is something akin to Pendulum's .start_of() method. https://pendulum.eustace.io/docs/#modifiers Given a certain DateTime, this would return a new DateTime at the start of some interval the original occurs in.

Time objects could probably implement .start_of() for second, minute, hour, and day, and Date objects could implement .start_of() for week, month, and year.

[ariebovenberg]

Makes sense. I've see end_of() being useful too. I'm mostly AFK this week so I'll have to come back to this later with a more in-depth analysis.

[spacemanspiff2007]

I'd love to see something like that because this a frequently used pattern throughout my code:

SystemDateTime.now().replace_time(Time(0, 0, 0), disambiguate="raise")

If it also could aslo be extended to hour, minute and second that would be very nice.

[ariebovenberg]

@spacemanspiff2007 for your use case start_of_day() already exists--although it won't raise on ambiguity.

[ariebovenberg]

A thought that just ocurred to me: start_of() is basically just round() with increment=1 and mode="floor" 🤔. The only thing missing is larger units (week, month, year) and an end_of() equivalent.

This would make an excellent addition to a "cookbook" of sorts in the docs...

[ariebovenberg]

Worth noting here: there's an example entry now demonstrating getting the "start of the hour": https://whenever.readthedocs.io/en/latest/examples.html#determine-the-start-of-the-hour