When you take an Astron out of swiss replica watches the box, it may have to be charged. The Astron is powered by light – any type of light will charge its battery, but sunlight is the most efficient energizer. The charging status is displayed via an "E – F" (Empty – Full) indicator between 9 and 10 o'clock. The power reserve when fully charged is two months in active mode and six months in sleep mode. In sleep mode, the Astron does not display the time until it "wakes up" by being exposed to light. It takes only six minutes of replica tag heuer sunlight to provide enough power for the Astron to run for one day, but going from empty to fully charged requires 65 hours of sunlight. The GPS receiver will not operate when the watch is low on power, so regular charging is important. The Seiko Astron performs two basic types of operations with GPS signals: it can automatically and manually sync to a single satellite to make sure its local time display is accurate, and it can be manually triggered to replica watches uk change time zones, which requires at least four satellite signals.The Astron automatically attempts to sync with a single GPS signal once each day. The sync can be set in motion by exposure to the sun or another strong source of light. The Astron's programming tells it that if a strong light source is present, there's a good chance it can receive a signal. If the Astron acquires a signal, it remembers when that happened. On subsequent days, if the watch is covered by clothing or otherwise blocked from light, it searches for the signal at the same time as the last successful attempt, assuming the chances for reception are good. To make sure it's always on time, the Astron can also receive leap-second data. Leap seconds are added about every 18 months to account for the Earth's slowing rotation. The most recent was added on June 30, 2012.