programmatic date/Time format for XY data

Is it possible to program the format of the Y part (Date and Time) as Date and Time? I can do this using Edit and select this option from the Format menu. When I import the data using LoadWave I can use the /B option to format the original data. However, I need to filter the data and create new XY pairs using a function and I can't fathom out how to program the Data and Time format.

My data are as XY pairs and I need to retain this because the time intervals are irregular.
My funding is such that I am still having to use version 5.05A :-(

I tracked down an earlier post which solved my issue.

Setscale d, 0, 0, "dat" , ydata