An IRIS serial date number is just a plain number that represents a particular date. You can create serial date numbers using the following functions (depending on desired periodicity):
Furthermore, you can use the usual colon operator to produce a specific range, such as
rng = qq(1990,1):qq(2010,4);
Finally, you can use the following functions to convert dates to strings and vice versa:
You needn't, in fact, care about the serial date numbers themselves too much, but for you info: The integer part of the serial date number is based on the count of periods from (a hypothetical) year 0, say N, whereas its decimal part carries information on periodicity: annual (N + 0.01), semiannual (N + 0.02), quarterly (N + 0.04), bimonthly (N + 0.06), monthly (N + 0.12), or indeterminate (N + 0.00).
Hence, if you type
x = yy(2000)you get a serial number 2000.01, while
x = qq(2000,1)produces 8000.04, i.e. a total of 8000 quarters from year 0 plus 0.04 to specify the periodicity.