The GameMaster shamelessly admits to having chosen the ratios of times to correspond reasonably well with the real world, thus avoiding tons of messy time conversions. That said:
An Urth "cycle" is fifty-six days long: twenty-eight days of light, followed by twenty-eight days of darkness. There are six such cycles in a year. A twenty-eight day period is referred to as a "month". A seven-day period is referred to as a "week". A day consists of twenty-four Turnings, periods represented by a magical hourglass. There are sixty minutes in a Turning, and sixty seconds to a minute.
Because there is no "night" and "day" in the traditional sense, life continues throughout the Turnings. Shops are open at whatever hours they see fit to be open, people sleep when they feel like it, and so forth.
Water is the most precious substance upon the planet. Thus, wealth is measured in terms of water. There are three types of coins in common use: the copper qaf, the silver jug, and the gold sol. Large quantities of money are usually carried around in the form of gemstones, though both silver and gold are occasionally pressed into the form of bars. The equivalency rates of copper, silver, and gold are equivalent to those in the Player's Handbook, and the amount of water they can be exchanged for is divided accordingly, with one silver jug being just that -- as much water as can be held in a typical jug, or roughly one gallon.
Coins come in various shapes and degrees of purity. The Djinn Lords and the Lich Lords all mint their own coinage, so even within a single city, there are likely to be several sources of coins flowing in. The coins are stamped with figureheads or symbols. Bars of silver and gold (usually 10 silver or 10 gold to a bar) are normally used only by merchants, and are usually stamped with the crest of the issuing merchant house.
Because this world is on a "water standard", not a "gold standard", the primary thing which causes coinage to be debased is not the purity of the coins themselves, but the fluctuations of the water supply.
The Water-Bearers are the closest thing that Urth has to an Adventurer's Guild. The Water-Bearers are essentially prospectors, hunting down new sources of water, and, usually, overseeing the initial construction and installation of projects to tap that water. The Guild might also guard threatened water sources. While the actual construction and maintenance of the Great Machines and the like are the province of the necromancers, the Guild usually is responsible for clearing out the area, securing it, making sure nothing disturbs the construction, and so forth.
The Water-Bearers travel far and wide. Their journeys take them to the ancient cities, so their secondary function is to serve as prospectors for potential sources of power and magical artifacts. They occasionally do courier work and other matters that require discretion, and the Guild is -- at least in theory -- entirely politically neutral.
The Guild does not have a monopoly upon water. Indeed, most often, the Guild follows up on leads that others discover, taking a contract on the behalf of the source of the information; the payment might be a flat fee, or a share of the proceeds, or both. The Guild operates only a few sources of water of its own; most discoveries made solely by the Guild are sold to a merchant house or similar interested party.
Some powerful people have their own water-prospectors that are not allied with the Guild. Indeed, members of the Guild sometimes choose to "go independent" after a time -- a move with both risks and rewards. Guild membership, though, means steady work (and rarely any worries about assassins).