After the death of a spouse, how long does the surviving spouse have to create a bypass trust in california?

There was a revocable living trust created with both spouses living. But one spouse is no longer living and a bypass trust has to be created.After the death of a spouse, how long does the surviving spouse have to create a bypass trust in california?
see a reputable lawyer to be sure it is done correctly, perhaps same one who wrot eup the living trusts.