This would be better posted on the legal forum, but…in NC there is no such thing as a “legal separation”. You can have a separation agreement between the parties that could possibly save you any aggrivations at the end of the one year one day required, but it is not necessary. You are separated the day that you begin to live separate and apart from one another with the intention of divorce.
There should be some sort of record; whether telephone connection, power connection, rental contract or even a witness if you have been staying with someone and would not have any of that. Any of these would prove date of separation but most of the time the courts go on your word.