How do you change snooze time on iPhone 5c?

Original answer: Go to settings, then menu settings , then scroll down to bottom of list and push center button when selector is on "snooze"

The above doesn't make any sense for the 5g Touch or Phone.

On these devices, the Snooze option is only available in the Clock alarms. The Calendar notifications do not have a Snooze option.

It appears that the only way to add a Snooze to a Calendar is to jailbreak the device. There are workarounds (look for Snooze Me as an option) but nothing that really allows snoozing outside of the Clock alarms.