How to create date from datetime (using lubridate)?

You can just use round_date

round_date(a, "day")
[1] "2014-01-02 UTC"

EDIT

You do need to be careful with rounding the time though. For complete equivalence here you would need to use floor_date.

identical(ymd("2014-01-01"), floor_date(a, "day"))
[1] TRUE

Using date() is much shorter and avoids any issues with rounding.

library(lubridate)
date(a)
[1] "2014-01-01"

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