Sigil Identification Papers

That's the part of the paper that should be notarized by some appropriately deputized basher at the Hall of Records. It oughta say something like "Witnessed here, this second day of the first rule of the state of Valiance in this 127th year FHR."

The cutter who made most of planewalker's lovely visual aids on the Sigil resources page schemed together a calendar system for the Cage, which you can find explained in full here. Basically, it uses seven days a week, three weeks (or Rules, each named after a planar axiom) a month, with seventeen months (or States, each named after a plane) a year. Even though the factions no longer hold power officially in Sigil, the way of measuring the passage of years is sometimes expressed according to the number of years that the current factol of the Fraternity of Order has held office. Hashkar being the factol during the publication of the Planescape line, he's the most commonly cited one, and being a dwarf petitioner (not common knowledge in Sigil), he was factol for quite some time. So the "FHR" part is referring to the current year of "Factol Hashkar's reign." I think that the "current" year in Planescape (according to planewalker.com's storyline) is the 127th year of Hashkar's reign. So, that line you point out is how obsessive graybeards keep time. Most bashers don't bother with all that fuss, however. This being a very official document, however, it's what you would write.

Planescape never had extensive detail on timekeeping on the planes, except for Sigil's unusual clock system ("four hours before antipeak," for example), so Ambrus's system is as good as any, especially since it's rather detailed and dovetails nicely with his gorgeous artwork.