How much value does an option lose each day?
An option's price includes time value: what the remaining days of possible movement are worth. Each day that passes takes some of it, if nothing else changes. For an option near the stock's price the daily loss is small with months left and grows as expiry nears. Brokers show this daily figure as theta: the formula's rate of loss right now, not a fixed charge. In the last day or two the real loss can be larger than theta says.
Try it: a call on a $50 stock, strike $50, priced at 30% implied volatility (made-up numbers). Move the days left.
Simulated example, priced by the StrikePath engine (Black–Scholes, interest 4.3% a year). For learning; not advice.
Why it speeds up near the end
With many days left, losing one of them changes little about what could still happen. With a few days left, each day is a large share of the time remaining, so it takes a large share of the value. That holds for options near the stock's price. An option far from it loses most of its time value earlier, so little is left for its last days.
What it means for a plan
A bought option gains only if the stock or implied volatility moves enough to outweigh this daily loss; a sold option collects it, and carries the risk of a sudden move. The course's lessons on time value and the practice flights let you feel both sides.
What this shows, and what it doesn't
It holds the stock price and implied volatility still. In a market both move every day, and a change in either can matter far more than one day's time value. This example counts every calendar day, weekends and holidays included. Some brokers count only trading days, so their daily figures differ.