I have a derived time-enabled mosaic dataset sourced from multiple mosaic datasets containing imagery grouped by year of acquisition. I'am trying to set the Allows Mosaic Methods to ByAttribute and use a new string field I've added to the attribute table named "Year". However, in the pull down menu the "Year" field is not listed. I've indexed the Year field and confirmed that is in enabled under allowed fields. I'm using desktop 10.5.1. Any ideas as to why the added Year field will not display as an option under byAttribute?