Working with dates and times is one of those things that sounds simple until you're staring at a timestamp column wondering why your "last 30 days" query returns unexpected results. Date and time functions are essential for analytics, reporting, and any application that tracks events over time — yet the subtle differences between database engines trip up even experienced developers. In this guide, we'll cover the most useful SQL date/time functions across PostgreSQL and MySQL — two of the most widely used databases — with practical, real-world examples. By the end, you'll know how to confidently filter by time ranges, calculate durations, group data by period, and avoid the most common pitfalls. Why Date/Time Functions Matter Think about how many queries involve time: "Show me orders placed in the last 7 days," "Calculate how long customers have been subscribed," "Group revenue by month." Nearly every meaningful business question has a temporal dimension.…