Board Thread:Manga/@comment-27938131-20170808181809/@comment-7278867-20170814075144

YEAR 820 - Zeke was born

827 - Zeke[7] Betrayed Grisha & Dina - Grisha & Dina sent to Paradise(?) - Grisha inherited the Attack Titan from Eren Kruger(?)

835 - Eren Jaeger was born

842 - Zeke[22] inherited the Beast Titan

843 - Reiner, Bertholdt, Annie & Marcel inherited the Armoured, Colossal, Female and Jaws Titan - Pieck inherited the Cart Titan(?)

845 - Fall of Shiganshina - Frieda Reiss killed by Grisha; Progenitor Titan inherited by Grisha - Eren[10] Jaeger inherited the Attack and Progenitor Titan; Grisha died.

850 - Battle of Trost - Zeke[30] infiltrated Wall Maria - Porco Galliard inherited the Jaws Titan; Ymir died(?) - Armin inherited the Colossal Titan; Bertholdt died.

Based on this, Grisha is a Titan Shifter between 827 to 845, for 18 years! 😨

This is according to the AoT guidebook