Sharing a issue which is common in almost all current versions of exchange(2007,2010 & 2013).
When user sends a meeting invite to other people ( We faced in case of all day event) with reminder set as none. On invitees end, after accepting the meeting reminder, it is set to default 15 minutes & goes off at 11:45pm.
On hub transport servers
1. Start Notepad.
2. Type the following in the Notepad file:
<?xml version="1.0" encoding="utf-8" ?>
<add key="AlwaysSetReminderONAppointment" value="false" />
3. In the File name box, type StoreDriver.config.
4. In the Save as type box, click All Files.
5. Save the file in the %ExchInstallFolder%\bin folder.
6. Restart the Transport service.
7. Repeat steps 1 through 5 on all Exchange 2007/exchange 2010/exchange 2013 servers that have the Hub Transport role.