Q. Shalom U’Bracha, Recently I purchased a Citizen eco-drive watch, that gets charged automatically from the light.

My question is: (1) Is it permitted to wear such a watch on shabbos (at home or within an eruv) when the watch has a reserve battery that can last about a year?

(2) This watch has a power save function “When the watch is continuously not exposed to light for 30 minutes … the second hand is automatically stopped to reduce the power consumption. The hour and minute hands operate continuously”

Would it be mutar to wear on shabbos, I noticed when I am sleeping (with my hand under the cover the seconds handle stops until I take it out.)

A. Many Poiskim permit the use of self-winding watches, while they are still working (see Shemiras Shabbos K’hilchoso 28:28). A watch that gets charged automatically from the light it receives and is ticking would also be permitted.

However Horav Shlomo Miller’s Shlit”a opinion in regards to the eco-drive watch you describe, is that it should not be used on Shabbos, since your covering or uncovering of the watch will have a direct effect and change the operation and functioning of the watch.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a