It is possible to set `MJD` of observation date-time in policy/teleSetting.yaml . However, if one changes the value from eg. the default "59580" to "59580.15" (forward by few hours to eg. avoid twilight light with quickbackground cmd option), then  the day of observation changes from 20211231 to 20220101 , but since the visitId is hardcoded, this leads to a failure (attached error trace). error_trace_MJD.txt

This is because when butler creates exposure and visit using define-visits , it includes, among other things, the obsDate in `YYMMDD` format, as inferred from the ingested raw data header) , but  ts_phosim  to  build a pipetask query uses a hard-coded visitId and obsId, such as

 self.visitIdOffset = 4021114100000

 obsId = 9006000

 exposure IN (\{self.visitIdOffset+obsId})

So that the first exposure number is always

4021114100000+9006000=4021123106000

This is confirmed by looking at the registry of the ingested raws:

butler query-data-ids . exposure visit --where "instrument='LSSTCam' "

which yields 

band instrument physical_filter    exposure       visit    

---- ---------- --------------- ------------- -------------

   g    LSSTCam               g 4022010106000 4022010106000

This ticket is to correct that behavior so that change of MJD in `teleSetting.yaml` does not lead to a failure.