I wrote a package that already supports this:

https://pub.dev/packages/flutter_chronos

print(Chronos.tomorrow()); // local time tomorrow 00:00:00

or

print(Chronos.parse('2025-09-13 10:35:00').ceilDay()); // 2025-09-14 00:00:00.000

if you need the day after tomorrow

print(Chronos.parse('2025-09-13 10:35:00').ceilDays(2)); // 2025-09-15 00:00:00.000

This package also provides many other date & time utilities

https://pub.dev/packages/flutter_chronos/example