The Sony A7 cameras have a lot of built in functionality. This is especially true of the A7s, which is the model I know best. Even though you can modify picture profiles, manually adjust audio levels and shoot in cropped mode, one function that the camera does not come with is an intervalometer or any sort of function that helps create time-lapse sequences. The good news is that you don’t have to buy a separate piece of hardware to be able to shoot a sequence of timed photos. All you need to do is buy the “Time-lapse” app from the Sony Play Memories store.
This app has a number of presets, like Cloudy Sky and Miniature, but also allows more control in a Custom option.
The most recent version of the app, offers a choice of creating a video file, simply creating a series of stills, or creating both. The easiest option for most people will be to create a video file in camera. Keep in mind, though, that the video will be 1920 x 1080 (16×9).
One thing to keep in mind when shooting a slow process, like for instance melting snow, is the battery life. The A7s is estimated to take 320 shots on 1 battery. If you set your interval for 5 seconds, your battery will, in theory, last less than half an hour (5×320=1600 secs or 26.67 minutes). This means you will need to change batteries before the process is complete. Chances are you will move the camera slightly. So, even if you stitch the video clips together, there will be some visible camera movement. Unfortunately, the A7s is not functional when plugged into a power source.
Here is a short video that should give you an idea of the process you need to follow to take your first time-lapse on the A7s. The process should be similar, if not identical, on other A7 models.