Neptune's years are 164.8 Earth years. Its days are 16 hours and 6.7 minutes long. Although Neptune's days are shorter than our days, its years are still longer than ours.
Most colorants will last in your pond approximately 30 days. You may have to add more pond dye before 30 days if you have execissive rainfall, run-off, a heavy out flow, or evaporation. If your colorant is fading you will visually be able to tell and should add more dye to the water.
Gels generally last 2-3 weeks. The best part about gel manis is how long they last. If you have a bunch of events coming up back to back like prom, internship interviews, and family vacays, gels can be the perfect solution because they last about two full weeks with no chipping. Keep in mind, thought, that how long they last does depend on your body chemistry, the product itself, and how it's applied.