Time Zone Calculator

How to convert a time between two zones with the time zone calculator

Every zone is described by how far its clock sits ahead of or behind Coordinated Universal Time, written as an offset like UTC-6:00. A conversion happens in two steps. The time you entered is first turned into a true UTC instant by removing the source zone’s offset, and that instant is then expressed in the target zone by applying its offset. The calculator above does both steps as soon as you press Calculate.

Worked example. Take 9:00 AM CST on 15 June, converted to EST. Central Standard Time is UTC-6:00, so 9:00 AM there is 3:00 PM UTC. Eastern Standard Time is UTC-5:00, so that same instant reads 10:00 AM in Eastern. The result is one hour later than the time you started with, on the same calendar day. Run the same conversion from PST at UTC-8:00 and the gap widens to three hours, giving 12:00 PM.

Offsets that are not whole hours work identically. India at UTC+5:30 and Nepal at UTC+5:45 are held in minutes internally, so converting 7:30 PM IST to EST returns 9:00 AM on the same day rather than an answer rounded to the nearest hour.

Pick the standard or the daylight version of a zone

The list offers EST and EDT as separate choices, and does the same for Central, Mountain and Pacific. This is the single decision that most often decides whether a conversion is right. Eastern is EST at UTC-5:00 through the winter and EDT at UTC-4:00 from the second Sunday in March to the first Sunday in November. Choosing the wrong one puts the answer out by exactly one hour, which is just plausible enough to go unnoticed.

Two zones in the list never move. What time zone is Arizona stays a genuinely two part answer: Mountain Standard Time all year (the MST time zone, not MDT), and Hawaii stays on UTC-10:00. Their gap to everywhere else therefore changes twice a year even though their own clocks do not, which is worth checking before scheduling anything recurring with either.

United States zones and the gaps between them

The four zones covering the contiguous states each sit one hour apart, running Pacific, Mountain, Central then Eastern from west to east. Alaska adds another hour behind Pacific and Hawaii another two.

Because the steps are even, the common conversions are easy to sanity check against the calculator. Central to Eastern adds an hour. Pacific time to central time adds two. Mountain time to eastern time adds two. Pacific to Eastern adds three, which is enough to push a 9:00 PM call onto the following calendar day. The full CST to EST conversion guide carries the complete matrix for every pair, along with the specific clock times people look up most.

Converting UTC and GMT into a local zone

UTC is the reference the rest of the offsets are measured against, and GMT describes the same offset for everyday purposes, so UTC to EST and GMT to EST produce the same answer. Both mean subtracting five hours while Eastern is on standard time, so 12:00 noon UTC is 7:00 AM EST. In summer the subtraction becomes four hours.

Anything scheduled in UTC before mid morning lands on the previous evening across North America, which is why the result panel names the weekday rather than showing a bare clock time.

More conversions at a glance

The presets above cover the pairs people convert most, but the same arithmetic answers dozens of other common questions. UTC to PST is a subtraction of eight hours in winter (12:00 noon UTC is 4:00 AM PST), and UTC to CST subtracts six. Going the other way, EST to UTC and CST to UTC both add the zone’s own offset back.

Between two named US zones: CST to PST subtracts two hours, and PST to MST adds one, since Mountain sits one hour ahead of Pacific. ET to CT, the informal way people write Eastern to Central, subtracts one hour, the same direction as EST to CST. Central time to Pacific time subtracts two hours the same way Pacific to Central adds two.

On daylight offsets specifically: PDT to EST adds two hours, EDT to EST is not a real conversion since both describe the same clock, and UTC to Eastern time (EST or EDT, whichever applies) subtracts five or four hours respectively. Two conversions people ask often by exact clock time: 9am CST to EST is 10:00 AM, and 8pm CST to EST is 9:00 PM, both the plain one hour addition from earlier in this page.

A few less common pairs: PST to Mountain time zone adds one hour, GMT to CST subtracts six, EST to UTC adds five, and CET to EST subtracts six. All follow the same two step method as the worked example above; the calculator handles every one directly, so this list is a quick cross check, not something to memorise.

Reading the result

The large figure is the converted time on a 24 hour clock, so 13:00 is 1:00 PM. The line under it names the weekday and the full date in the target zone, which is the part worth checking rather than skimming. A conversion of three hours or more will regularly land on a different day, and a meeting booked on the right hour of the wrong day is harder to catch later than one booked an hour out.

Underneath, a short line states whether the result is on the same calendar day, one day later, or one day earlier than the date you typed, and repeats which zone it refers to. If something cannot be converted, that line turns into an error naming the problem instead, and the figure stays blank rather than showing a number worked out from a value the calculator could not read.

The swap button between the two dropdowns reverses the direction without retyping anything, which is the quickest way to sanity check a conversion. Convert one way, swap, and the result should return to the time you started with. The preset buttons underneath jump straight to the pairings people look up most, including CST to EST, PST to CST and UTC to EST.

How the zone list is organised

Zones are grouped by region rather than listed as one long alphabetical run, so the United States and Canada block sits first, followed by Europe and Africa, Asia and the Middle East, Australia and the Pacific, then South America. Each entry shows the abbreviation, the full name and the offset together, because the abbreviation alone is not always enough to identify a zone.

That last point matters more than it looks. CST means Central Standard Time in North America and China Standard Time in Asia, fourteen hours apart, and IST is used for India, Ireland and Israel. Showing the offset beside every abbreviation removes the ambiguity at the point of choosing. The conversion guide lists the other collisions worth knowing about, and the final group holds the plain UTC offsets for anyone who already knows theirs.

What this calculator does not do

It converts between the two zones you select. It does not look up what time it is somewhere right now, and it does not decide whether a date falls inside daylight saving, since that mapping changes by country and sometimes by year and a table of those rules goes stale quietly. Asking you to pick EST or EDT keeps the arithmetic exact instead of guessing on your behalf and being confidently wrong twice a year. Most devices show the current offset in their clock settings if you are unsure which applies.