Time zone is the way of organizing time in regions of the planet, based on a “reference time” (such as UTC) and applying offsets.

The main practical challenge is that some places change the offset throughout the year due to local rules (daylight saving time), and these rules can change over time.

Practical example: a meeting at 10:00 in São Paulo may fall at different times in Lisbon depending on the time of year (seasonal changes). That's why it's better to convert by city/region than by a fixed offset.

Use this converter to plan meetings, deadlines and trips, avoiding “guess” errors when involving different countries.

Tip: always confirm the date with the time. “10:00” without a date may give different conversions in different months because of daylight saving time.