Get the begin time of a half-hour period, that is denoted by its end time.
fGetBeginOfEddyPeriod(Time.V.p, DTS.n = 48L)
Time stamp in POSIXct time format
Daily time steps
The timestamp of an Eddy record denotes the end of a half-hour period. This function gets the time, half an hour before
integer vector of length(Time.V.p): of times shifted by half an hour.
TW (Department for Biogeochemical Integration at MPI-BGC, Jena, Germany)