docs(input-schema-specs): add example pattern regex for full ISO date… (#1353)

See discussion:
https://apify.slack.com/archives/C01E7CSJ2PP/p1734018697179259

Not sure if this is the best place to put it.

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Co-authored-by: Michał Olender <[email protected]>

Author: metalwarrior665

sources/platform/actors/development/actor_definition/input_schema/specification.md

@@ -244,6 +244,14 @@ When using escape characters `\` for the regular expression in the `pattern` fie
 
 :::
 
+#### Advanced date and time handling
+
+While the `datepicker` editor doesn't support setting time values visually, you can allow users to handle more complex datetime formats and pass them via JSON. The following regex allows users to optionally extend the date with full ISO datetime format or pass `hours` and `minutes` as a relative date:
+
+`"pattern": "^(\\d{4})-(0[1-9]|1[0-2])-(0[1-9]|[12]\\d|3[01])(T[0-2]\\d:[0-5]\\d(:[0-5]\\d)?(\\.\\d+)?Z?)?$|^(\\d+)\\s*(minute|hour|day|week|month|year)s?$"`
+
+When implementing time-based fields, make sure to explain to your users through the description that the time values should be provided in UTC. This helps prevent timezone-related issues.
+
 ### Boolean
 
 Example options with group caption: