I'm not sure about Mexico, but Canada and USA switched to Daylight Saving Time on March 11. If your Smallworld system times are off by an hour, please read "USA/Canada Daylight Saving Time is 4 weeks longer this year. Are you ready?"
You can tell if you have the appropriate Smallworld patch loaded by executing the following command at the Magik prompt.
If the date and time are different than you expect, it is likely that your patch has not been loaded.
An e-mail from the Smallworld helpdesk also mentioned that the most recent time zone patches include adjustments for Western Australia.