Stop Date Columns Adding Time Value (Bug?)

So I’ve been having a problem with a Schedule to Buffer Zap, which seemed to be occasionally ignoring the specified time for a tweet and just “inventing” one (often with seemingly arbitrary minute values).

The value uses a DateTime column to tell Buffer when to schedule (as that’s what Buffer needs), but in the Coda doc this is formed by adding together a Date column and a Time column (thereby allowing us to use the Calendar selection dropdown to pick dates, which isn’t available on true DateTime columns).

It turns out, the problem is caused by the Date column adding both a date and time when a Date is selected from the Calendar dropdown. From what I can see, that time is the current PST time when the action is taken. When my formula then adds the Date and Time columns to create my scheduled Datetime, that initial extra value is causing it to go wrong.

Weirdly, if the Time column already exists, then this isn’t a problem; it only happens when Date is filled first, then Time, which is why it was only happening sporadically.

Does anyone know of a way to prevent the time from being added to the Date column? I’m sure that I can come up with a workaround, but this will always be unwanted behaviour for Date columns that I create (otherwise I’d just use a Datetime column to begin with) so would prefer a less costly fix.