A question regarding the weekly timeframe

I’ve noticed that when you open a chart and set it to the weekly time frame, the candlesticks always indicate that they began on Sunday at 0:00. But after closer inspection I’ve noticed that the candlestick pops up only at Monday 0:00. What’s even stranger is that the Sunday candlestick on the weekly time frame has the Open price of the Monday candlestick. What gives?

Edit: To anyone else using Oanda, did you notice a spike of more than 1500+ pips on EUR/USD last week?