Timepicker conflicts with end date settings

Problem/Motivation

We're using the jQuery UI Timepicker (https://fgelinas.com/code/timepicker/) to set time on date fields, and the change in 7.x-2.11 to set end dates to 23:59:59 (for example) is going to be a significant issue. We use the timepicker because users want fast data entry, and they never need more granular time settings than :00, :15, :30 and :45.

After running the 7.x-2.11 database updates, we saw end dates were shifted one day ahead and 14 minutes, 1 second back. So an end date of "2020-01-01 06:00:00" became "2020-01-02 05:45:59". I'm not sure how this issue can be rectified, because those using a timepicker are very, very rarely going to enter seconds other than :00. This means there would need to be some type of convoluted conversion to extract "2020-01-01 05:59:59" from the database and display it as "2020-01-01 06:00:00" so the timepicker works correctly.

I'm sure you've been researching this a long time and have a better grasp on how to approach the larger problem of date storage. At a high level it seems to make more sense to store data as major times as it has been (06:00:00 instead of 05:59:59), and handle the differences in the front-end display. Users won't be intuitively entering and/or editing dates of 1 second differentials.

I am certainly open to discussing further and sharting ideas, or if another path needs to be taken, this issue can be closed. Thanks.