Some things to note about the time format. It sets up 3 different fields automatically and on submit, checks to see if it is a time and puts the 3 fields together into the field you specified in the fieldname attribute (in 24 hour time format).
Here is a list of some of the tags you can use with time:
Please note that if you do choose to use a default value and use Now(), make sure you set the minuteinterval to 1 or you will get some errors.