The other things I have on the page (eg Hertz 5 Star) say 31/12/23, so looks like it's standard rather than US dates for me, but I guess it could be account region specific? 4th Jan is a slightly funny date to pick, whereas I guess 1st April would be a year from when it was issued? In case it's helpful, generally with these certificates it's a 'book by' rather than 'stay by' date, the only issue is it is effectively non-refundable past the date (as you just lose it rather than it being refunded).
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