Timestamp before/after format

If I write a message with like so: "The event starts <t:1677672000:R>!", it will be rendered (at the time of posting) "The event starts in 3 months!" After it's over though, the message will say "The event starts 3 days ago!", which doesn't look right anymore. I'd like a timestamp format extension that lets me pick out two possible text messages depending on if it's before or after the timestamp. My proposal is to use ?, like a ternary operator in many languages. It could look like this: The event <t:1677672000:?:starts:was> <t:1677672000:R>!" Would render "The event starts in 3 months!" or "The event was 3 days ago!" depending on if the time passed or not.