Convert an object of class Date to class POSIXct without getting bogged down in timezone calculation.
DateToPOSIX(timestamps)
YearMonToPOSIX(timestamps)Calling as.POSIXct on another date/time object
(e.g. Date) applies a timezone correction to the object. This can
shift the time marker by a few hours, which can have the effect of
shifting the day by one unit. If the day was the first or last in a
month or year, then the month or year will be off by one as well.
Coercing the object to the character representation of a Date prevents this adjustment from being applied, and leaves the POSIXt return value with the intended day, month, and year.