If you choose to divide it like that, script 1 is the one that needs to know about DST, because user 123 might be 9 UTC today, but what is it tomorrow? Might c

If you choose to divide it like that, script 1 is the one that needs to know about DST, because user 123 might be 9 UTC today, but what is it tomorrow? Might change due to a DST change (which varies by time zone, and time zone DST date can change year-to-year), or the user might change time zones. Either way, your Script 1 is the logic that had the bug I inherited.