Format the datetimestamp column of SWMP data
Value
Returns a POSIX vector if tz_only
is true, otherwise the timezone for a station is returned as a chr string
Details
This function formats the datetimestamp column of SWMP data to the POSIXct
format and the correct timezone for a station. Note that SWMP data do not include daylight savings and the appropriate location based on GMT offsets is used for formatting. This function is used internally within data retrieval functions and does not need to be called explicitly.