Six years is very good for battery life. Mine rarely get past 3. Not in the Volvo.

As others have attested, the pulsing parasitic drain is from the quartz clock. Other sources of parasitic drain are the ECU computer, radio memory and airbag. Generally, this drain won't kill a healthy battery that's fully charged over several months.

Here is an excerpt from a GM bulletin on how much parasitic drain a battery will tolerate:

"Here are some rules of thumb that might help relate parasitic drains to how long a battery would last on a parked vehicle. The Reserve Capacity (RC) rating multiplied by 0.6 gives the approximate available ampere-hours (AH) from full charge to complete rundown. Somewhere between full charge and complete rundown, the battery will reach a point at which it can no longer start the engine, although it may still operate some of the electrical accessories.
Using up about 40% of the total available AH will usually take a fully-charged battery to a no-start condition at moderate temperatures of 25°C (77°F). Put another way, for a typical battery in a storage situation, depleting the available AH by 20 to 30 AH will result in a no-start condition."

I'd say 'Farm Boy' has guessed right. I put an ammeter on the large clock in one of our 240's and you could see the current (a few milliamps) pulsing with the clock's ticks. Presumably the 700/900 clocks are the same or very similar. The radio will draw a tiny amount of current to keep its memory of preselected stations, audio settings, etc., alive.
--
Bob (son's 81-244GL B21F-M46, dtr's 94-940 B230FD, my 83-244DL B23F-M46, 89-745(LT1 V8), 98-S90, 77MGB and four old motorcycles)

Yes it would be the clock and/or radio taking little bites of juice. If it barely lights up your test light (assumimg very low power bulb and not a tail light bulb or something) then you could ignore that power draw, it is normal.
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David Hunter

Mechanical clocks in car dash clusters sometimes use a spring. A periodic pulse of electricity winds the spring and then it runs for a few seconds before requiring another pulse. I cannot say if Volvo's work this way.