What modification means
A modification is a court-approved change to an existing custody or support order. Orders are meant to be stable, so courts generally will not revisit them on a whim: most states require a substantial change in circumstances since the last order before they will consider modifying it.
That standard is inherently about patterns over time, which makes it a documentation question. Demonstrating a substantial change usually means evidence spanning months, not a single bad week. A consistent record is what lets you show a genuine, sustained shift rather than an isolated flare-up.
Example: seeking to adjust a schedule because the other parent has repeatedly failed to exercise their time is far stronger when you can present six months of dated entries showing the pattern, compared with a complaint based on the last two weekends.
What counts as a substantial change, and the process for requesting one, varies by jurisdiction, so let your attorney assess whether your documented pattern meets the local threshold.