On the tile, yearly returns are calculated based on the returns for the stock or ETF from 1 year ago.
For example, if Google's share price was $700 1 year ago and its now $900, the year return would be $200/$700, which is 28.57%. For newer stocks, like SNAP which have not traded for a full year, the return is based on the close price on the first day of trading.
For day change, this is based on the current or last price (if the market is closed) subtract the previous close price. In both instances, you can find the actual $ and % move on the Details page for each share.