Times for multiple users don't align in Outlook calendars when opened by one user

When our receptionist opens several users calendars side by side, using the daily view, on her desktop outlook the times don't always align.  This occurs with all staff within our organization and isn't specific to any one calendar as the problem is random. This causes appointments to be scheduled in the wrong time slot.  This problem just started a few months ago.  Any suggestions for fixing are welcome.