Markers - Optimise map marker timestamp filtering

[johnb432]

When merged this pull request will:

• Title
• Probably could do it better with regex, but I'm not willing to go down that road.

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[rautamiekka]

I probly could make a RegEx, but someone will have to explain (with example values) this SQF. I suspect someone else will figure it out by then, though.

[LinkIsGrim]

It'd be a simple regex but I don't wanna think about it