[m] When does a Hague Convention enter into force?

In general, the entering into force of a Hague Convention requires the deposit of three instruments of ratification, acceptance or approval (cf. e.g. Art. 46 (1) of the 1993 Intercountry Adoption Convention).
Thereafter, for each State ratifying, accepting or approving it subsequently, or acceding to it, the Convention enters into force three months after the deposit of instruments of ratification, acceptance or approval or accession (cf. e.g. Art. 46 (2a) of the 1993 Adoption Convention).

N.B.: Not all the Hague Conventions follow the general rule explained above. Hence, to obtain a reliable answer here, each Convention must be verified separately. You can do so by clicking on Conventions and then consulting the Final Clauses of the particular Convention you are interested in.