Can regex be used in an operation to generate the first second of the day (or last second) from a pure date?

[JozefAerts]

For checking whether a collected data point (e.g. variable LBDTC), e.g. 2026-08-25T08:24 is between a start date and an end date like usually provided in SVSTDTC and SVENDTC (like 2026-08-23 and 2026-08-24) we need to transform the start date to 2026-08-23T00:00:00 (begin of day) and 2026-08-24T23:59:59.
As I understand it, this could e.g. be done using a regex:
$T00:00:00
or $T23:59:59
In https://cdisc-org.github.io/cdisc-open-rules/#/operations?id=record_count we find an example where something like that is used with "group", but it is not clear whether the "regex" can also be used without group, like in:

• operator: start_of_day
  id: $xxx
  regex: $T00:00:00

Otherwise I think I am going to write a function in Python taking care that "00"-s are added until it is a complete datetime, and anoth that takes care that a date (without time part) is transformed to the last second of the day by adding "T23:59:59".

Man thanks in advance!
Jozef

[pendingintent]

With SDTM data, we cannot make assumptions. Only collected values can be used. If no time is collected, we cannot assume/impute a time value for the observation.

If the time was supposed to be collected at the time of observation, the EDC should enforce the rule and an edit check should catch this before preparation of the SDTM domains.

The regex will not add a value to the DTC value but will filter:

import re
match = re.search(r'T(.*)', "2026-08-23T00:00:00")
print(match.group(1))  # "00:00:00"

If you wish to add assumed values to your collected observation dates, you should do this in you own code and prior to evaluation with the CDISC Open Rules.

[JozefAerts]

Ok, thanks!
I am currently working on the Python code (functions) to be able to check whether a collected date is within the window of a visit date (from SV). As, unfortunately, sponsors have the bad habit of only added date without time, this means that in the Python code, for SVSTDTC, we must add the time part to the start of the day (i.e. 2026-08-23 => 2026-08-23T00:00:00) and, for SVENDTC, to the end of the day (e.g. 2026-08-25 => 2026-08-25T23:59:59).