Every state's standard form, and the deadlines it triggers

The date the last party signed, also called the acceptance date, the date of ratification, or mutual acceptance depending on the state's form. Every period-based deadline in a contract counts from this date, which is why it's the one field the engine always requires.

It depends on the contract's stated basis: calendar days count every day, business days skip weekends and holidays. When a computed deadline lands on a weekend or federal holiday, the engine rolls it forward to the next business day, except the final walkthrough, which rolls backward so it can't slip past closing.

No. They are common starting values for the standard form most resales in that state use, not any specific contract and not a legal requirement. Standard forms leave these periods blank for the parties to fill in, and riders routinely override them. The only number that matters is the one on the executed contract.