Positing date automatically change today even manual date added

1

While posting date in Sales Invoice and Purchase Invoice is automatically changed to today’s date although the previous date entered is past date.
The date is not changed manually but system is automatically updating the date to current date

Date change
Date change1420×786 149 KB

Date change 1
Date change 11420×786 132 KB

2

you have to check “Edit posting date and time” else it will keep updating posting date and time until you submit it.