Just received NEW information from Gates regarding date codes!! The first Gates Tech rep said two weeks ago that my belt (purchased from Pelican) stamped 4353DS was made in 2013, fourth digit indicating year of manufacture. I then ordered three additional belts from two other sources looking for a newer code.
Today, after pushing a bit on the 435 part of the number (having read in an earlier post that the first three digits indicated day of the year, so how come "435"?) today's Gates rep paused, then checked with higher authority and came back to say that for timing belts, the code is different ... the FIRST digit is the year and the next three indicate the day, so my first belt was made in December 2014! Their serpentine belts use the former code however, thus their confusion.
BTW, another wierdism in this story, one of the belts was noticeably thinner between the teeth than the others. My crude calipers indicated 2 mm thich vs ~ 2.6+ mm for the others (less rubber on the smooth side). A bit of a QC problem here (and i did mention this to the Gates rep.
All's well that ends well I guess, but what a mess getting there.