It was shortly after he was elected. His staff told him to sign it, and he never took the time to consider it before signing it.
That is just BS. I happen to know that he was deluged with telegrams and letters from every Catholic Church in CA asking him not to sign it and warning him about the outcome. If he "didn't take time to consider it" that means that he was just giving the back of his hand to all the Catholics in California, in addition to the other religions who oppose abortion as a matter of conscience.
In my own parish, the priests furnished us with directions on how to send a telegram the Sunday before he signed it into law. Can you imagine the lily-livered Pastors doing that now? "Oh, Lord, they'd say. The IRS will take our tax deductions away, or maybe a parishioner will stop giving to the building fund."
We didn't have much money then and 4 little children, but my husband and I sat down and drafted a telegram designed to put our thoughts within the 10 word limit for the cheapest rate. Others wrote lengthier treatises.
As a matter of fact, in the letter which he sent me weeks later, he claimed that he had "considered it carefully". So who are you going to believe? Someone who was there and involved, or somebody who writes about the past with rose colored glasses? Was he lying then, or are his biographers lying now?