How do I protect employees against entering time/expenses in BillQuick that are incorrect, like entering January 2018 instead of 2019?
To overcome this problem to a great extent, 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 BillQuick if the time entry date falls beyond (before or after) the number of days specified here. This defines the number of days into the past and the future allowed for saving or deleting a time entry. BillQuick 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 5/18/2018 and you enter 365 in both text boxes, BillQuick will not allow you to make time entries older than the year 5/18/2017 and beyond the year 5/18/2019, assuming that you have unchecked the 'Allow Adjust Beyond Global Setting Restriction' permission in Security.
You can grant selected users permission to enter and edit dates outside this period by adjusting their Security settings. This setting can ensure that employees record or edit their time within the days specified by you; for example, 7 days before or after the current day.