Fixed date format

`date:"%Y-%m-%dT%H:%M:%SZ"` outputs invalid dates like `2014-09-21T17:28:15Z`
`date_to_xmlschema` is used for other dates in the same file and outputs dates in the [right format][1] like `2014-09-21T17:28:15+05:30`

[1]: http://www.w3.org/TR/NOTE-datetime