Yes, the delay occurs approximately 2-3 minutes, as mentioned by @nathanaelb. This is an old issue that can be addressed with tolerance communicated to the user (using a slight mathematical formula to subtract 5 minutes from the deadline). Of course, the condition is to use the ‘extra-sync mode’ option. However, there’s a small note that can be a bit unsettling: ‘All syncs in extra mode count as updates, even if no data has changed.’ 
Yes @Jeff_Hager, using the API is the most accurate way to get the remaining time duration, although this will consume updates based on the number of clicks. Meanwhile, fetching the ‘now’ data is heavily dependent on the synchronization timing between Glide and the spreadsheet, which won’t update without user activity in the app (unless you choose extra sync options). The middle ground is implementing two conditions, relying on the user’s device time and considering the condition of the ‘Now’ from the spreadsheet, which generally has some delay. While waiting for a resolution regarding the ‘Now’ from Glide.
If you need midnight on the first day of the month, the above can be expanded as follows:
Now
-DAY(Now)+1
-HOUR(Now)/24
-MINUTE(Now)/1440
-SECOND(Now)/86400
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