Calls for an equal childcare contribution from each of the parents involved with a child completely miss the mark, as childcare is only a subset of the work required in the production of a new human being. Pregnancy, breastfeeding (if applicable), and childcare are all work. The time – the work – one of the parents spends pregnant and breastfeeding should therefore be offset by an equivalent amount of work spent caring for the child from the other parent(s). Men should do more childcare than women.
For the numerical specifics I cede the floor to someone more knowledgeable in the area, but for the sake of example we’ll take 11 weeks which is how long, in the United Kingdom, maternity leave can start before the due date. An equitable share in the production of a new human being would then have the father or other parent taking over sole care of the baby for 11 weeks (or possibly longer if breastfeeding is involved) after it is born, or after an agreed upon time. Thereafter both parents would share equally in the work.
Pregnancy, the biologically necessitated involvement in the pre-birth production of a child, for women, being far greater than that of men, offers a compelling case as one of the causes or reasons for the emergence of patriarchy in its current state (and the relative absence of matriarchies). The involvement of men in the production of a child is dependent on the cultural and the economic situation, but biology means that women will always have a minimum level of involvement as they are the ones who have to go through the birthing process.