The Canary Islands use the 24-hour clock, which can be quite confusing for those who are accustomed to 'am' & 'pm'.
Gran Canaria and its neighbouring islands maintain Greenwich Mean Time (GMT/UTC, which makes it identical to the UK but one hour behind most European countries and mainland Spain.
In March, the clocks are put forward one hour for daylight saving time. Clocks are put back one hour on the last Sunday in October.
Converting from AM/PM to the 24-hour clock:
between 12:00 AM and 12:59 AM, subtract 12 hours: 12:59 AM --> 00:59
between 1:00 AM and 12:59 PM, a straight conversion: 10:00 AM --> 10:00
between 1:00 PM and 11:59 PM, add 12 hours: 10:59 PM --> 2259
Converting from the 24-Hour clock to AM/PM:
between 00:00 and 00:59, add 12 hours: 00:59 --> 12:59 AM
between 01:00 and 11:59, straight conversion to AM: 01:00 --> 1:00 AM
between 12:00 and 12:59, straight conversion to PM: 12:59 --> 12:59 PM
between 13:00 and 23:59, subtract 12 hours: 15:59 --> 3:59 PM
We recommend that you do not drink tap water as it tends to be desalinated seawater. The locals almost all invariably drink bottled water.
Water from public fountains should not be drunk unless there is a sign saying Agua Potable. You will often see signs saying Agua No Potable, Water Not Drinkable. In bars, supermarkets or restaurants, ask for ‘agua sin gas’ (still) or ‘agua con gas’ (sparkling).
Some hotels do ask for co-operation when it comes to water consumption (for example, to put the towels out to wash every two days instead of doing it daily).