The local currency is the American dollar (USD). All major credit cards are accepted everywhere. There are ATMs everywhere as well and exchanging money is easy, however the rates at home in UK seem to be better than in the States, so do some research prior to travelling. Most banks and exchange shops also tend to charge commission. Most travellers prefer to withdraw money from their debit cards via ATMs, but if you decide to do that, make sure you have called your bank to say you would be abroad, and also are aware of any fees your bank may charge you for using your card abroad.Opening hours and bank holidays. Most independent shops of Honolulu are open all week from 9 am to 6 pm. Banks and post offices would be open 9 am until 5 pm weekdays and would work until midday Saturday as well. The outlets near Waikiki beach, markets and tourist-related shops will be open as late as 10pm. There are a few bank holidays in Hawaii, and the banks and post offices will be closed, however most shopping malls and other outlets will work as normal.Tipping culture is huge in Hawaii, as in the whole of the USA. As a general rule, you should tip any service staff. Many of them are paid low hourly rates and rely heavily on tips. Between 15 and 20% of the bill at a restaurant is considered normal but beware that some establishments include it in your bill, especially for larger groups. Hotel staff should also be tipped about a dollar per bag for the bellboy and about 2 USD per day for the housekeeper. Taxi drivers and spa saloon staff expects between 10% and 20% of the bill. Bartenders expect about a dollar per drink, more if the place is more upscale, and tour guides anything from 15 to 20%, depending on the length and the size of the group.The local time in Honolulu is GMT-10 hours and the dialling code is +1 808.