x <- as.POSIXct("2009-08-03 12:01:59.23")
round_date(x, "second")
# "2009-08-03 12:01:59 CDT"
round_date(x, "minute")
# "2009-08-03 12:02:00 CDT"
round_date(x, "hour")
# "2009-08-03 12:00:00 CDT"
round_date(x, "day")
# "2009-08-04 CDT"
round_date(x, "week")
# "2009-08-02 CDT"
round_date(x, "month")
# "2009-08-01 CDT"
round_date(x, "year")
# "2010-01-01 CST"
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