This is the case where the wife won the CA lotto, but never told the husband, and they
were married apparently, when she bought the winning ticket, and had not yet separated.
https://law.justia.com/cases/california/court-of-appeal/4th/90/34.html
Fiduciary duties between spouses may end up in a breach of fiduciary duty, especially where the financials are not listed in the divorce documents.
Thus if one won the CA lotto, one would supposedly list that one had won the lotto, on the proper forms, since it occurred during the marriage and would have to be listed on the forms that we use for dissolution, under the asset/debt sections.
Eventually, the husband found out accidentally, that the wife had won the lotto, and he filed a motion to set aside the divorce decree, and for damages for the wife's fraud and breach of fiduciary duty. Unfortunately for the wife--the court ordered her to give all of the lotto winnings, 100%, to the husband.
The separation date was thus crucial, because once the parties separate, all the earnings and everything acquired after date of separating, are then normally --- the separate property of each spouse.
----> But the separation date isn't just for lotto wins--- reimbursement claims relating to payment on separate or joint debt, or in fixing rights to real property can come into play. CA law provides the community does have an interest in appreciation of an owned residence, such as where title is only in one spouse's name--the spouse owning the property could plausibly argue that the appreciation belongs only to that spouse--and there are a number of facts that could impinge on that theory. The separation date can also impacts the principal loan amounts. Businesses which were established before or during marriage which continue to derive income after separation can be impacted (valuation, up or down,etc.) Importantly , the date of separation is of huge impact for spousal support, or alimony rights. Its continuation or termination is of huge concern due to the length of the marriage.