When searching Issues or Pull Requests in Github, can you specify a date relative to "today"?

The search API may have been updated since this original question, but you can limit date ranges by duplicating the exclude params.

-created:<=2018-01-01 -created:>=2018-03-31 {other params...}

If you only want anything newer than 2018, then you can leave out the first part, e.g.:

-created:>=2018 {other params...}