There is no definitive answer to this question as it largely depends on what type of slot player you are. For those who are just starting out and are looking for a fun and easy way to gamble, playing online slots at night or during the weekends is generally the best time to do so.
This is because there are generally more players online at these times, which makes for a more enjoyable experience.
For more experienced slot players, however, there is no definitive answer. That said, many experts believe that playing slots during the day when most people are at work is the best time to do so because there is less competition and chances of getting frustrated.
Ultimately, it all comes down to personal preference and what works best for you.
