Hi Andy
Do you have audit enabled in your environment for login events?
https://techdocs.broadcom.com/us/en/symantec-security-software/identity-security/identity-manager/14-5/configuring/auditing/configure-and-generate-audit-data-report.html
<AuditEvent name="Login" enabled="true" auditlevel="BOTHCHANGED">
<AuditProfile objecttype="USER" auditlevel="BOTHCHANGED"/>
<EventState name="COMPLETE" severity="NONE"/>
<EventState name="INVALID" severity="CRITICAL"/>
</AuditEvent>
<AuditEvent name="Logout" enabled="true" auditlevel="BOTHCHANGED">
<AuditProfile objecttype="USER" auditlevel="BOTHCHANGED"/>
<EventState name="COMPLETE" severity="NONE"/>
<EventState name="INVALID" severity="CRITICAL"/>
</AuditEvent>
If this is in place, you could potentially run a query on the audit database and search for those users who did login within your preferred time range as explained in https://knowledge.broadcom.com/external/article/13116/how-to-extract-user-login-information-fr.html
As a side note, while not quite you have asked for, re modify date - you should be able to use the ever so detailed information here https://community.broadcom.com/communities/community-home/digestviewer/viewthread?MID=794002 to see the value of last modification in the modifyTimeStamp operational attribute.
Hope this helps
Regards
Rinat