Evidently the various calendar systems have been ‘harmonised’ in such a manner that (I presume) according to our calendar it would’ve been on the 1st May 1006,

Evidently the various calendar systems have been ‘harmonised’ in such a manner that (I presume) according to our calendar it would’ve been on the 1st May 1006, which I take literally to mean something along the lines of “May 1st 2023 was the 1017th annual anniversary of the event”.