Given an OffsetDateTime, how to find the beginning of the current month and beginning of the next month?

[discosultan]

For example, given an OffsetDateTime ("2020-12-26T21:02:00Z"), how to:

1. Get an OffsetDateTime that represents the beginning of the current month ("2020-12-01T00:00:00Z")?
2. Get an OffsetDateTime that represents the beginning of the next month ("2021-01-01T00:00:00Z")?

With Chrono crate, I was able to achieve this using the DateTime::date, DateTime::from_utc, Date::with_day, Date::with_time, Date::from_ymd APIs. Haven't figured it out for this crate yet.

[jhpratt]

On the assumption that chrono's DateTime is the same as time's OffsetDateTime:

You can get the year, month, and day by calling OffsetDateTime::to_calendar_date. To get the beginning of the month, call OffsetDateTime::from_calendar_date Date::from_calendar_date with the day set to one. For the next month, you can use Month::next and set the day to one. For that, you'll have to manually adjust the year (should be as easy as checking if the month is December).

[discosultan]

Thanks, that did the trick! Just a note that OffsetDateTime::from_calendar_date should be Date::from_calendar_date instead. I then constructed an OffsetDateTime by using Date::with_hms and PrimitiveDateTime::assume_offset.

[jhpratt]

Ah, right. I typed it off-hand without thinking about the specifics.