t0prd = myTime / aim_surfForc_TimePeriod
tmprd = t0prd - 0.5 _d 0 + tNcyc
_RL t0prd, tNcyc, tmprd, dTprd
_RL t0prd, tNcyc, tmprd
tmprd = MOD(t0prd,tNcyc)