Very good question. Whenever the judge makes such an order, there is no way to calculate the accurate amount of timeshare each parent spends with the child on a prospective basis. That means that you will need to keep a log of when and how long you visit with your child as that will be used to calculate child support.
As you likely already know, child support is primarily based on 2 factors: the relative income of the parents and the amount of time each spends with the minor child. The less time you spend with the child, the more child support you will pay.
If the court ordered "at-will" or "reasonable" visitation, the only way to calculate timeshare in the future is to guess. And what will inevitably happen in these types of situations is that mom will say you don't exercise the amount of time you are claiming. So, be prepared to present evidence to the judge when the issue comes up.
For more information about child support and other family law related issues, please see the links below. Good luck to you.
If you found this answer helpful, let me know by clicking the "Mark as Helpful" button or "Best Answer" at the bottom of this answer. By answering this question, the Law Offices of Cathleen E. Norton does not intend to form an attorney-client relationship with the asking party. The answers posted on this website should not be construed as legal advice. The Law Offices of Cathleen E. Norton does not make any representations about your family law matter, but rather, seeks to provide general information to the public about family-law related matters. You should consult with an attorney to discuss the specific facts of your case. Thank you.