Dear @sanket252 are you running a live/production version of Primero? If not, could you try installing and running Primero v2 instead of v1.6 since we have a more up-to-date software with regular releases with v2?
The issue is with the date format. Make sure they are in UTC format. From the docs
date field shall be of the form 1995-12-31T23:59:59Z The trailing “Z” designates UTC time and is mandatory Optional fractional seconds are allowed, as long as they do not end in a trailing 0 (but any precision beyond milliseconds will be ignored).
Did you try stopping and then starting solr?
Either use rake stop/start or just kill the PID. You could also try removing the solr folder after stopping and before starting and it should regenerate (not tested so do at your own risk)
The only thing I can think of (apart from upgrading) is grepping through the database looking for dates without the Z at the end. So a value of “2020-10-10 23:59:59+0300” should be expressed as “2020-10-10T20:59:59Z” for solr
Can you find out which dates it works/fails on? I guess some dates managed to get into the db in a form solr does not like so you need to find and edit them. It should be pretty obvious I think which they are