Currency and Calendar
To keep things simple this game will use the currency from the PHB and calendar from the World of Greyhawk

Currency
200 copper = 1 gold
20 silver  = 1 gold
2 electrum  = 1 gold
5 gold  = 1 platinum

Greyhawk Calendar

7 Day festival - Needfest, Feast of Fools
28 day month - Fireseek
28 day month - Readying
28 day month - Coldeven
7 Day festival - Growfest
28 day month - Planting
28 day month - Flocktime
28 day month - Wealsun
7 Day festival - Richfest (Midsummer Day, Holy Day of Pelor)
28 day month - Reaping
28 day month - Goodmonth
28 day month - Harvester
7 Day festival - Brewfest
28 day month - Patchwall
28 day month - Ready'reat
28 day month - Sunsebb

Days of the Week:
Starday - work (1st,8th,15th,22nd of each month and festival)
Sunday - work (2nd,9th,16th,23rd of each month and festival)
Moonday - work (3rd,10th,17th,24th of each month and festival)
Godsday - worship (4th,11th,18th, 25th of each month and festival)
Waterday - work (5th,12th,19th,26th of each month and festival)
Earthday - work (6th,13th,20th,27th of each month and festival)
Freeday - rest (7th,14th,21st,28th of each month and festival)

The adventure begins 575 Common Year of Reckoning...

Date: Freeday, 28th Day of Wealsun.  The day before a 7 Day festival - Richfest (Midsummer Day, Holy Day of Pelor)