I was wondering if using calendar other than Gregorian (Jalali or Persian calendar to be exact) is going to influence SEO, and is the Google is able to recognize such dates?
Well as a person that I have used Jalali calendar a lot in my websites and even I have a website for converting Gregorian calendar to Jalali (keye.ir) there are two things to consider:
If your content is in a language that is related to the calendar you use its better to use the relative calendar. For example if your website language is in Persian its better to use Jalali calendar because if a person searches for something in Farsi he will more probably use Persian date in his search query than using Gregorian calendar. Other examples would be if a user is checking to see when is Ramadan he will be using Hijri Year, If want to find out about Salary raises in new year in Iran he will use Persian Language and Jalali year and ...
If your website is multi-language you would better be using relative calendar for each language and for that if your content is generated dynamically you should save the Gregorian date in your database and convert it to Jalali or Hijri or what ever calendar is related to the content when generating the content.