Time is mandatory if the date is set in the Key Result check-in modal

Issue Summary

In both legacy and new experience objectives, when checking in on a Key Result you receive the message 'Please enter an amount and a date' if you do not enter a time even if the date was set.
Also, you see an incorrect set by default '18/2/1993' instead of the current date.

Steps to Reproduce

1. Go to an objective
2. Add Key Result of type Score for example (same happens with other types)
3. Click on the check-in button
4. An incorrect default date '18/2/1993' appears when the Key Result check-in modal opens so the users feel the need to change it.
5. Set the value accordingly, enter a text in the node, and set a date without the time

Expected Results

The correct default date for today appears when the modal opens so the users don't feel the need to change it and/or if the date is changed the Key Result new value is saved regardless of the time.

Actual Results

The Key Result new value is not saved and the error message 'Please enter an amount and a date' appears.

Here is an animated gif showing the behavior:

Workaround

Make sure to not touch the date before saving if you want the automatic timestamp to be used else select a time at the same time as the date.