Is there any way for this timer to be programmed to turn on at sunset and turn off 6 hours later? There doesn’t seem to be a way to do that with this device.

Thank you for your question. No, the 81670 does not offer an “offset timer” that allows setting an OFF time relative to dusk. There’s no integrated feature to say “dusk + 6 hours,” and no separate programming slot adjusts automatically on that basis. You could determine your latest expected dusk time (e.g., 5 PM) and manually program the OFF time accordingly. However, this means the OFF schedule won’t follow seasonal sunset variations.