Greetings Ekta,
Are you in a data migration scenario?
The Data and time you require is the data and time of the physical installation of the Equipment in the Functional Location. Therefore, if you are migrating the data for an existing installation, which was erected some time ago, and there was no Equipment management process, then this should be the same as the installation start-up date. Same for the Functional Locations.
But if you are migrating new Equipments, then you should obtain actual installation dates to reflect the reality.
Sometimes, it may not be feasible to get the original installation dates from the plant. You may have to give an arbitrary date. In that case, please ensure that the date is no later than your go-live date for Maintenance Processing in SAP, or no later than any Historical Orders that you want to migrate for that installation and Equipment - so you do not run into issues with installation time segments.