Yes, you are absolutely right. Though I did not follow the price chart but about one year ago I noticed that every Sunday Bitcoin price starts decreasing and Monday it goes low about 200-500 USD at least, and on Wednesday to Friday Bitcoin's price grows again. Maybe it's because Sunday is a holiday in most of the country, so people cash out crypto money on Sunday and that impact on Bitcoin price on Monday, so, when the price is low, that's the buying time without any doubt.