initial time to set when (re)-starting a simulation with Venus PCM

[emillour]

If a simulation was not run for an integer number of days than one must be careful to set

## si less1day is y and if successive runs are made,
## then indicate here the fraction of the initial day for the previous run
## !! and also set raz_date=1 !!
## Default=0.
starttime=.... 
raz_date=1

in run.def , where starttime is the correct fraction of day.

But in principle this should be automatic; the time of day at which the previous run ended should be stored in the start file(s) and simply re-used (when raz_date=0)

To be further investigated and corrected.

=> should be fixed with r3615