Add time in search string

Hi All, i want to add time in search string. My data is showing time 26-02-2018T02:00:00.000+0000, but while searching i want to add 11 hour , means it should create filter for time 27-02-2018T13:00:00.000+0000. Also after this i also want to apply substring on time to just show dates. i am using below one, but its not working. index=XXXXXX source="XXXXXX" |eval host=add(Date,+11) | eval hostgroup=substr(Date,1,10) | stats count(Date) by hostgroup Please help. Vikash