Another way.
There is a random list of times in column A of the attached. Some cells are "blank".
In column I is the list not containing blanks. The formula entered in cell I1 and filled down until you get blanks is an array formula. If you aren’t familiar with array-entered formulas array enter means the formula must be committed from edit mode by simultaneously pressing and holding down Ctrl and Shift while hitting Enter.
Then the attached uses D1 for the drop down. Data validation 'Allow:' is List. 'Source:' is
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