yes, It is possible to change datetime in email template. Please use the below code sample in your email template. It will work.

${(datetime.datetime.strptime(object.date_start,'%Y-%m-%d %H:%M:%S') + relativedelta(hours=5,minutes=30)).strftime('%Y-%m-%d %H:%M:%S')} 

Above code will add +05:30 in date_start datetime.

Hey Nilesh,

Thanks much. This really worked for me. I just replaced the body_html code at four places in the meeting invite email template, with your code and it works great.

Existing code:

${object.event_id.get_interval(object.event_id.start, 'dayname', tz=object.partner_id.tz)}

Replaced with your sample code:

${object.event_id.get_interval(((datetime.datetime.strptime(object.event_id.start,'%Y-%m-%d %H:%M:%S') + relativedelta(hours=5,minutes=30)).strftime('%Y-%m-%d %H:%M:%S')), 'dayname', tz=object.partner_id.tz)}

Basically replace "object.event_id.start" with 

"((datetime.datetime.strptime(object.event_id.start,'%Y-%m-%d %H:%M:%S') + relativedelta(hours=5,minutes=30)).strftime('%Y-%m-%d %H:%M:%S'))"

First instance is for 'dayname', the other is for 'day', next for 'month' and finally 'time'.