Trade finance tenors run for weeks and months, and the tenor sets both the cost and the risk window
Tenor is the time from the start of a trade finance deal to its maturity. A 2010 ICC-ADB study put average tenors for short-term products between 53 and 256 days. Interest builds up by the day, so cost scales with tenor.
Every trade finance price is a rate for a number of days plus fees, and the currency sets the day count
A trade finance rate is a base rate for the tenor plus a margin for risk. The charge builds up for each day the money is out, over a year length set by the currency: Actual/360 for US dollars, Actual/365 for sterling. Fees come on top.