ceiling_date behavior should fit the intuition at boundary

[shrektan]

Issue Description

As discussed in #262, the ceiling_date behaves strangely at the boundary (i.e., the first date of a month or a quarter), as documented in ceiling_date,

By convention the boundary for a month is the first second of the month. Thus floor_date(ymd("2000-03-01"), "month") gives "2000-03-01 UTC".

Current behavior

lubridate::ceiling_date(as.Date("2016-03-01"), unit = "month")
# [1] "2016-03-01"
lubridate::ceiling_date(as.Date("2016-03-02"), unit = "month")
# [1] "2016-04-01"

What users might expect

However, the users (at least myself) would naturally expect the two lines above return the same value 2016-04-01.

[vspinu]

One solution would be to define boundary for all units being uniformly 00 not 00 for some (hour, minute, second) and 01 for others (day, month). In that case yyyy-04-01 will be ceiled to yyyy-05-01.

This would mean that day and month don't have a boundary which implies at least two bad things. First one being that floor(ceiling(...) is not the same as floor, second is that ceiling(ceiling(...)) for a date jumps over two months. This is a major change and might break current code in quite unexpected ways.

So I am thinking to add a new argument to ceiling_date. Maybe ceiling_on_1 or no_boundary? Other ideas? If, TRUE, ceiling behaves as you propose. If FALSE, it's the current behavior. This might be a global option which you can set with options once per session.

[vspinu]

I have settled on change_on_boundary (defaults to FALSE). Please let me know if you think the argument name can be better. Thanks.

[shrektan]

@vspinu Thanks. Naming is really hard... I think change_on_boundary is very clear for me, but if I can come up with something more concise I'll let you know 😃

[mr-teu]

Thanks, ran into this issue literally 5 minutes ago!

[vspinu]

Just letting you guys know that there is no global option for change_on_boundary anymore. See #443 for the reference. Just make a wrapper function if you are bothered by typing the option every time.