I had an HTC Desire about a year ago but had to sell it.
I use the calendar function a lot on my Nokia phone,
The problem I had with the Desire is as follows:

Suppose I set a calendar alarm to remind me to check my cars tyre pressures every Sunday morning at 10.00am.
Every Sunday at 10.00am the alarm goes off. Ok so far.
If for instance it is raining that Sunday morning or I am too busy to check the tyre pressures there and then , if I try to change that day's alarm for 3.00pm on the Sunday afternoon instead, it won't let me do it without changing all the following alarms to go off on Sunday at 3.00pm too!
I am not sure which Android version my Desire had but do the newer Android versions let you change an alarm like I need it to be changed?
Thanks for any replies.