To convert Text column to Date column format in Sharepoint column

Suppose you have a column(named,"DateText") with text format and the value it returning is of type datetime("2009-06-18T00:00:00"),
To convert it into datetime format(mm/dd/yyyy),

first create a calculated column named Expiration Date, with datatype as datetime and with the follwing formula:

=IF(ISNUMBER(FIND("T",[DateText])),TEXT(LEFT([DateText],FIND("T",[DateText])-1),"mm/dd/yyyy"),TEXT([DateText],"mm/dd/yyyy"))

Then create one more calculated column with DateTime data type and use the following formula:

=DATE(YEAR([Expiration Date]),MONTH([Expiration Date]),DAY([Expiration Date]))