I've had a few people ask me about time syncing cameras during events such as weddings. These large shoots can often call for multiple photographers, in multiple places with multiple cameras. Of course, it would be great to meet with everyone before the event and dive into the camera menu system and sync the all the clocks together. We see it all the time in movies, especially with bank robberies themed shows.
However, it's much easier than you think and each person can sync their camera clock to a known standard. We can call it Apple Standard Clock. We are not sure if this works the same on Android or other phones, but I think it should since the majority (if not all) phones sync automatically to the cell service. Basically, it means that everyone's phone should have the same time displayed, right down to the second - or within a sec. Each photographer need only to shoot a pic of their phone screen where the hours, minutes and seconds are displayed. This way allows the editing photographer to shift the camera time stamp to a standard, making everyone's camera timeline the same.
Here is a video that might help understand the process in Lightroom after the wedding. In this video, each photographer shoot an image of the same iPhone with an app that displays seconds. If I would have thought about it before hand, I could have easiely asked them to install that app before leaving home.
Here are a few apps that show seconds to time sync your camera. If you have any suggestions, please add them to the comments below.