Iphone 10 birthday calendar in Chinese

Iphone birthday calendar suddenly switched to an Asian language. No other part of the calendar or other apps were affected. After over 10 hours of support, attempts to fix it failed. Checked location, region, language. Reset the data and no luck. The last hope was to do a factory reset on the phone and then add back in texts, calendars, etc.(according to support). The phone was reset, no choice was given for a back up date except yesterday (which did no good) needed to go back a couple months. Was told by support that there would be an opportunity to add back in the texts, calendar, etc. Well, that didn't happen. Now phone is factory reset, all contacts, texting, apps and especially the birthday calendar are gone! What would be the next step to restore that calendar?