YEARFRAC(S, E[, B])

Description
Returns the year fraction representing the number of whole days between S (start date) and E (end date). This function is useful in calculating the percent of benefit or obligation to assign a specific period.

Parameters
S
A date value that represents the start date

E
A date value that represents the end date

B
(Optional) The day count basis to be used:
0 or omitted 30/360
1 Actual/actual
2 Actual/360
3 Actual/365

Examples
YEARFRAC(DATE(94, 1, 1), DATE(94, 5, 30), 0) = 0.4167

YEARFRAC(DATE(94, 1, 1), DATE(94, 5, 30), 1) = 0.4110