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You could use the default DateTime field that we have under our "Quick Tools" section to let your users to pick up dates with minutes and hours on them.
1. Click the DateTime field and click the "Time" to enable it.
2. To change the increments on minutes, let's say per 10 minutes, you can change it on the "Properties" of the DateTime field.
You may also want to check a couple of widgets we have related to calendars here: http://widgets.jotform.com/category/pickers.
Do let us know if this helps.