[Feature] 13665 date time format not respected

[``* `#13665` Date/Time format not respected``](https://www.openproject.org/work_packages/13665)
[``* `#13664` Timezone not respected``](https://www.openproject.org/work_packages/13664)
this ``date-time`` tag will not be replaced and I suppose we don't want it as a tag within the markup (do we?)