If USCIS considers the child less than 18 years of age when a parent naturalizes as a U.S. Citizen or a step parent submits a family petition so the child can get a green card, then your application/petition will be successful. However, if USCIS considers the child over 18 your application/petition will be denied.
We may think these are a very simple situations with no problems but it can be very complicated and difficult to fix. This is especially true when the child is in another part of the world where the time zone and date are different from the time zone and date in the United States.
Generally under the law, courts will not consider differences in the times zones or fractions of a day. The only time a court will consider this question is when it affects an important right. Petitions to get a green card and being considered a U.S. Citizen may be considered important rights. However it depends on what part of the U.S. you are in and what U.S. Court of Appeals is in that area.
The reason for this problem is that the wording of the immigration laws in the above situations is unclear. If you and your child are in one of these situations it is possible to get a denial of your petition or application fixed. An Immigration Attorney should be able to help you with this.
Please contact a licensed Immigration attorney before you act on your specific situation. Immigration Laws and Federal Regulations are constantly changing and the general information provided can change over time.