Core datetime_range fields currently require both a start date and end date OOTB. However, the idea that one or both of these could be optional has been accepted in principle by core subsystem maintainers in ✨ Allow end date to be optional Needs review , and is available in contrib in the optional_end_date module.
Smart date's formatters currently don't support this possibility on datetime_range fields, but very easily can.
Currently SmartDateTrait causes the formatters to make no attempt to process a core daterange field value unless it has both a start and end date.
Let's change this so that only one of them is required.
Needs review
3.6
Code
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It's likely this issue predates Contrib.social: some issue and comment data are missing.
In my use case, I have legacy values in old events where only the start time is known, not the end time. I use the core widget for these events, but the smart date formatter.
I'm not sure why this change is needed considering the work in #3192815: Support optional dates in core datetime_range fields → that has already been merged in and released. In fact, looking at the code it looks redundant to the code implemented there.