GMT to CST
-6hGMT
GMTSOURCECST
CSTGreen rows indicate typical business hours (9 AM - 5 PM)
GMT and CST on the World Map
The map below highlights the GMT (Greenwich Mean Time) and CST (Central Standard Time) timezone regions across the globe.
GMT – Greenwich Mean Time
UTC+00:00Greenwich Mean Time (GMT) is the mean solar time at the Royal Observatory in Greenwich, London. It is the same as UTC+00:00.
- •GMT is based on the Prime Meridian (0° longitude) passing through Greenwich, London.
- •The Royal Observatory in Greenwich has been the reference point for GMT since 1884.
- •GMT and UTC are often used interchangeably, but UTC is based on atomic clocks.
- •Iceland uses GMT year-round and never observes daylight saving time.
- •The UK switches from GMT to BST (British Summer Time) in late March each year.
CST – Central Standard Time
UTC-06:00Central Standard Time (CST) is the time zone for the central United States, Canada, and Mexico, 6 hours behind UTC.
- •CST covers 20 US states fully or partially.
- •Chicago and Houston are the two largest cities in the Central Time Zone.
- •Mexico City, one of the world's most populous cities, operates on CST.
- •CST is 1 hour behind EST and 2 hours ahead of PST.
Understanding the -6h Gap: GMT vs CST
GMT runs on Greenwich Mean Time (GMT) at UTC+00:00. CST runs on Central Standard Time (CST) at UTC-06:00. That puts GMT 6 hours behind CST — a difference of -6h at the current offsets.
In practice, when it is 9:00 AM in GMT it is 3:00 AM in CST. Midnight in GMT is 6:00 PM in CST. Neither zone observes daylight saving time, so the offset between them stays constant all year.
GMT to CST time conversion table
| GMT (GMT) | CST (CST) | Day |
|---|---|---|
| 12:00 AM | 6:00 PM | previous day |
| 6:00 AM | 12:00 AM | same day |
| 7:00 AM | 1:00 AM | same day |
| 8:00 AM | 2:00 AM | same day |
| 9:00 AM | 3:00 AM | same day |
| 12:00 PM | 6:00 AM | same day |
| 3:00 PM | 9:00 AM | same day |
| 5:00 PM | 11:00 AM | same day |
| 6:00 PM | 12:00 PM | same day |
| 9:00 PM | 3:00 PM | same day |
Why people convert GMT to CST time
- Scheduling a call from GMT to CST: a 10:00 AM start in GMT lands at 4:00 AM in CST, so you can confirm the slot without doing the arithmetic yourself.
- Finding shared working hours: both GMT and CST are inside the 9-to-5 working day between 3:00 PM and 5:00 PM GMT time (9:00 AM–11:00 AM CST). That is roughly 2 hours of usable overlap.
- Booking travel or deliveries: tracking CST local time against GMT keeps pickup windows and arrival estimates honest across the -6h offset.
- Always state the zone abbreviation, not just the hour. "3:00 PM GMT" is unambiguous; "3 PM" across a -6h gap is not.
- Block 3:00 PM–5:00 PM GMT as the recurring meeting window if you work primarily from GMT and need CST colleagues present.
About GMT (Greenwich Mean Time)
Greenwich Mean Time (GMT) is the clock time at the Royal Observatory in Greenwich, London, which sits on the Prime Meridian (0° longitude). GMT serves as the reference point from which all other time zones are calculated. The United Kingdom uses GMT during winter months and switches to British Summer Time (BST, UTC+01:00) from late March to late October. Several West African nations use GMT year-round. GMT is often used interchangeably with UTC (Coordinated Universal Time), although technically they are different – UTC is based on atomic clocks while GMT is based on Earth's rotation.
About CST (Central Standard Time)
Central Standard Time (CST) covers the central region of North America. It is the second most populous time zone in the US, including major cities like Chicago, Houston, and Dallas. CST is also used in Mexico City and much of Central America including Guatemala, Honduras, El Salvador, and Costa Rica. During summer, most of the US and Canada switch to Central Daylight Time (CDT, UTC-05:00), while Mexico and Central American countries generally remain on CST.
Best time to call between GMT and CST
Both GMT and CST sit inside the 9 AM – 5 PM working day between 3:00 PM–5:00 PM GMT, which is 9:00 AM–11:00 AM CST. That gives roughly 2 hours of shared time — the safest window for a live call or meeting.
Business hours overlap
GMT and CST overlap for about 2 hours during the working day — enough for meetings if you avoid the edges of the window.
GMT is 6 hours behind CST (GMT UTC+00:00 → CST UTC-06:00). The shared working window is 3:00 PM–5:00 PM GMT. Remember to re-check around daylight-saving transitions.
🕐 Daylight Saving Time Info
GMT
☀ Currently in DST
Standard: UTC+00:00 · DST: UTC+01:00
Clocks fall back on Sun, Oct 25, 2026
CST
☀ Currently in DST
Standard: UTC-06:00 · DST: UTC-05:00
Clocks fall back on Sun, Nov 1, 2026
Learn More About Time
Dive deeper into the fascinating world of timekeeping, time zones, and how they shape our global society:
Frequently Asked Questions
What is the time difference between GMT and CST?
GMT (GMT, UTC+00:00) is 6 hours behind CST (CST, UTC-06:00). The gap is currently -6h.
How do I convert GMT time to CST time?
Add -6h to GMT local time. For example, 9:00 AM in GMT is 3:00 AM in CST.
What time is it in CST right now?
CST uses CST at UTC-06:00. Use the live converter at the top of this page — it updates in real time and already accounts for the -6h offset from GMT.
What is the best time to call CST from GMT?
Call between 3:00 PM and 5:00 PM GMT — that maps to 9:00 AM–11:00 AM CST and keeps both parties inside the working day.
Which is behind, GMT or CST?
GMT is 6 hours behind CST. When it is 12:00 PM in GMT it is 6:00 AM in CST.
Does daylight saving time affect the GMT–CST difference?
Neither zone observes daylight saving time, so the -6h offset between GMT and CST is fixed all year.
Which other cities share GMT's time zone?
GMT also covers London, Dublin, Lisbon, Accra, Reykjavik, Edinburgh, Casablanca, Dakar and 5 more.
Which countries use GMT, GMT's zone?
GMT is used in United Kingdom, Ireland, Iceland, Portugal (mainland), Ghana, Senegal, Mali, Mauritania and 7 more.
Is there a day difference between GMT and CST?
Not normally. The -6h gap only pushes the date over the previous day.
What is the time difference between GMT and CST?
CST is -6h from GMT.
What timezone is GMT in?
GMT operates on its local timezone.
What timezone is CST in?
CST operates on its local timezone.
Which countries use GMT (Greenwich Mean Time)?
GMT is used in United Kingdom, Ireland, Iceland, Portugal (mainland), Ghana, Senegal, and 9 more countries.
Does GMT observe daylight saving time?
Yes, GMT switches to BST during summer months.
What are some interesting facts about GMT?
GMT is based on the Prime Meridian (0° longitude) passing through Greenwich, London. The Royal Observatory in Greenwich has been the reference point for GMT since 1884.
Which cities are in the CST timezone?
Major cities in the CST timezone include Chicago, Houston, Dallas, San Antonio, Mexico City, Austin, Winnipeg, Memphis.
What is the UTC offset for CST?
Central Standard Time (CST) is at UTC-06:00. During daylight saving time, it shifts to CDT.
What should I know about the CST timezone?
CST covers 20 US states fully or partially. Chicago and Houston are the two largest cities in the Central Time Zone.
When is it midnight in GMT, what time is it in CST?
When it is 12:00 AM (midnight) in GMT (GMT), it is -6h later in CST (CST).
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See every conversion from GMT →·See every conversion from CST →