How do I prevent employees entering time and expenses in Core for incorrect dates, like May 2017 instead of 2018?
To overcome this problem, you can set the option 'Time entry should not be saved/deleted if older/newer than' in the Global Settings screen. Time entries will not be saved in Core if the time entry date falls beyond (before or after) the number of days specified here, say 365. This defines the number of days into the past and the future allowed for saving or deleting a time entry. Core rejects a date more than or less than those number of days.
This setting works in combination with the 'Allow Adjust Date Beyond Global Setting Restriction' security permission. For instance, if today's date is May 18, 2018 and you enter 365 in both text boxes, Core will not allow anyone to make time entries older than the year May 18, 2017 and beyond the year May 18, 2019, assuming that you have unchecked the 'Allow Adjust Beyond Global Setting Restriction' security permission. Similarly, if you want that employees record or edit their time within a week of the current date, you can enter 7, e.g., 7 days before or after the current day.
You can grant selected users permission to enter and edit dates outside this period by adjusting their security settings.