Change colons to periods in date/time field

[#1]

I am trying to change colons to periods in time in a date/time field. Instead of 12:22:36 I need it to be 12.22.36. I have tried everything I can think of- I can do it when it is just a time field. I tried concatenating a date field with the correctly formatted time field and it reverts back to colons in the concatenated field. Any help would be greatly appreciated- we are trying to save the file with a date and time stamp and Windows does not accept colons in file names. This is an example of the issue I am having:

[#2 · Accepted solution]

here is how it works for me:

The following is set as patterns for the time field:

Use the pattern time{HH.MM.SS} for Display option and if it is interactive also use in Edit.

Then set the calculate script of the text field as follows:

Javascript: DateField1.formattedValue + " " + TimeField1.formattedValue

That gets me this result:

[#3]

What method or script do you currently use to fill the Save File As-field?