Reason for setting LAYP_STDATE environment variable in the CMAQ runscript

I was wondering what happens to the CMAQ inline emissions when LAYP_STDATE environment variable value is not set in the CMAQ runscript, but values of LAYP_STTIME and LAYP_NSTEPS variables are set.

I am seeing that the LAYP_STDATE, LAYP_STTIME and LAYP_NSTEPS environment variables are all commented out in the ‘CMAQ_Project/CCTM/scripts/BLD_CCTM_v532_intel/RUNTIME_VARS.F’ file of CMAQv5.3.2: