Zulu to IRST Time Converter

Convert Zulu (UTC+00:00) to IRST (UTC+03:30) instantly.

Convert Zulu Time to IRST

Convert Zulu (UTC+00:00) to IRST (UTC+03:30) instantly.

Input Base Time

Target Timezone

Local Result

12:00 AM GMT+3:30

Live Visualization

Live Global Clock

Syncing

Current Zulu Time

12 3 6 9

16:27:05

May 25, 2026 UTC +00:00

Timezone intelligence

Zulu to IRST Timezone Map

Visual UTC offset relationship, day and night split, and live timezone context for Zulu and IRST.

UTC gap: +3h 30m

Iran Standard Time (IRST) is 3 hours 30 minutes ahead of Zulu Time (UTC) (Zulu)

Updated: 16:27Z

Zulu 16:27 UTC

GMT+3:30 19:57 GMT+3:30

Difference +3h 30m ahead

Source

Zulu Time (UTC) (Zulu)

UTC+00:00 | UTC

16:27 UTC

Target

Iran Standard Time (IRST)

UTC+03:30 | GMT+3:30

19:57 GMT+3:30

Relationship

Iran Standard Time (IRST) is ahead of Zulu Time (UTC) (Zulu)

Ahead/behind delta: +3h 30m

DST: Standard (GMT+3:30)

Offset band

UTC+0 Zulu Reference

Offset: UTC+03:30

Local: 19:57

DST: Standard

Day and overlap tools

Day/night UTC offset map

Zulu line highlighted

Blue tiles are night and warm tiles are daytime. Source and destination offsets are outlined, and UTC+0 is emphasized.

Meeting overlap visualizer

Work hours

Overlap guidance appears from the selected source and destination timezones.

Reference table, analytics, and history

Reference Grid

Dynamic conversion table

From	To	Zulu

Timezone Intelligence

Timezone detail panels

IANA references, live offsets, DST status, and offset history for both selected zones.

History Tools

Conversion history and favorites

Save frequent timezone routes and instantly replay your recent conversions.

Saved pairs

Recent conversions

Route Overview

Zulu to IRST overview

Primary route

The time difference between Zulu and IRST is exactly 3 hours and 30 minutes. IRST is ahead of Zulu. For practical purposes: when it is noon (12:00) in Zulu, the time in IRST is 15:30. When it is midnight (00:00) in Zulu, IRST reads 03:30.

Common paired routes: IRST to Zulu , Zulu to IRDT , and Zulu to AZT .

Zulu

UTC+00:00

Zulu Time (UTC)

IRST

UTC+03:30

Iran Standard Time

Operational Use

Operational use cases

SaaS companies with engineering in Worldwide (Aviation, Military, Maritime) and sales in Iran synchronize sprint ceremonies using this conversion.

Legal teams file international patent deadlines using Zulu timestamps, which local counsel must translate to IRST.

Oceanic route planning mandates Zulu timestamps for waypoint ETAs; crews based in IRST perform this conversion pre-flight.

ATIS (Automatic Terminal Information Service) broadcasts in Zulu require local interpretation by IRST-based tower operators.

NATO DTG (Date Time Group) format uses Zulu as default; liaison officers in IRST zones must decode incoming messages.

Drone surveillance patrol schedules originate in Zulu and require conversion for ground control stations operating in IRST.

Technical Brief

Technical details

UTC offset explanation

Zulu Time (UTC) (Zulu) operates at a fixed offset of UTC+00:00. Iran Standard Time (IRST) maintains an offset of UTC+03:30. The net difference between these two zones is 3 hours and 30 minutes—meaning IRST is ahead of Zulu by this amount. When converting, you add 3 hours and 30 minutes to get the equivalent IRST reading.

Daylight saving behavior

IRST does observe daylight saving time. During summer, clocks advance to IRDT (UTC+04:30), reducing the gap with Zulu by one hour. The transition dates vary by jurisdiction but typically occur in March/April (spring forward) and October/November (fall back). Confirm current DST status for time-critical operations.

Additional notes

In the NATO military time zone system, Zulu is designated by the letter "Z" and IRST corresponds to "—". These single-letter codes appear in Date Time Group (DTG) formatted messages used across all NATO member forces.

Iran Standard Time is the civil time standard for approximately Iran. Major cities operating on IRST include business, aviation, and governmental hubs that require constant coordination with UTC-referenced systems.

Cloud infrastructure providers (AWS, Azure, GCP) log events in UTC/Zulu by default. Engineers troubleshooting incidents in IRST regions must convert log timestamps to correlate with local observations. A 3 hours and 30 minutes mental adjustment is required for every log entry.

The non-integer hour offset of IRST (UTC+03:30) adds complexity to automated scheduling systems. Many cron-based tools and calendar applications handle whole-hour offsets natively but require explicit configuration for 30-minute fractional zones.

In-Depth Guide

Everything you need to know

Iran Standard Time

Zulu Time to Iran Standard Time (IRST)

Iran Standard Time (IRST) is the official time zone observed across **Iran**. Positioned at a fractional offset of **UTC+3:30**, IRST is exactly **three hours and thirty minutes ahead of Zulu time**. Following a legislative shift in September 2022, Iran permanently abolished daylight saving time (DST) adjustments, making UTC+3:30 the year-round standard.

Conversion Logic

Understanding the Fractional Zulu to IRST +3:30 Offset

Quick Reference

Zulu to IRST Hourly Conversion Chart

This table converts standard Zulu times into Iran Standard Time (UTC+3:30). Late evening Zulu times at or after 20:30Z roll over into the next day (`+1 Day`) locally in Tehran.

Zulu Time (Z)	IRST (UTC+3:30)	Day Change?	Standard Operational Context
0000Z	03:30 IRST	Same Day	Early morning operations / prep
0400Z	07:30 IRST	Same Day	Tehran local business day start
0800Z	11:30 IRST	Same Day	Midday slot management / peak cargo transits
1200Z	15:30 IRST	Same Day	Afternoon flight departures / terminal shift handover
1600Z	19:30 IRST	Same Day	Evening regional traffic wave
1800Z	21:30 IRST	Same Day	Late night scheduling / airline turnarounds
2000Z	23:30 IRST	Same Day	Pre-midnight gate operations
20:30Z	00:00 IRST	+1 Day	Midnight transition — shifts calendar date
2100Z	00:30 IRST	+1 Day	Early morning overnight arrivals
2300Z	02:30 IRST	+1 Day	Pre-dawn transit slot monitoring

Mental Math

Mental Math Steps: Converting Zulu to IRST

IRST is 3 hours and 30 minutes ahead of Zulu (UTC). Since this is a fractional timezone, use this structured mental calculation routine:

Add 3 Hours to Zulu Hour Start by adding 3 hours to the Zulu hour value. For example, if it is 10:15Z, add 3 to 10 to get 13.

Add 30 Minutes to Zulu Minutes Add 30 minutes to the Zulu minutes. In our example: 15 + 30 = 45. Thus, 10:15Z becomes 13:45 IRST.

Resolve Hour Overflow (>60 min) If the minutes sum is 60 or greater, subtract 60 minutes and add 1 extra hour (e.g. 10:45Z + 3h 30m = 13:75 = 14:15 IRST). Finally, if hours exceed 24, subtract 24 and increment the day.

Geographic Zones

Regions Observing Iran Standard Time

Islamic Republic of Iran Observed uniformly across all provinces. The timezone reflects Iran's geographic span over the Iranian plateau.

Tehran Imam Khomeini Airport (IKA / OIIE) The main international gateway. Flight slots, customs schedules, and gate assignments coordinate via UTC+3:30.

Tehran FIR (OIIX Airspace) A high-traffic regional FIR linking traffic corridors. Control handovers are scheduled globally using pure Zulu standard time.

Edge Cases

Essential Zulu to IRST Conversion Rules

Fractional Offset Addition (+30 mins): Remember to add both the hours and the minutes (e.g. 10:40Z + 3h 30m = 13:70 = 14:10 IRST). Carefully carry the overflow.

Date Rollover starts at 20:30Z: Because IRST is 3.5 hours ahead of Zulu, the local day rollover occurs at exactly 20:30 Zulu time. Any flight plan timestamped at or after 20:30Z represents the next calendar day in Tehran.

DST Permanent Abolition (2022): Iran abolished daylight saving shifts in September 2022. IRST stays permanently at UTC+3:30 all year round, simplifying summer flight operations.

Aviation Focus

Tehran FIR (OIIX) Airspace Coordination

Tehran Air Traffic Control manages high-level transit routes linking Europe with East Asia and the Persian Gulf. Pilots and dispatchers synchronize transit points entirely in Zulu time, while local ground logistics map to IRST.

Tehran FIR (OIIX) High-altitude overflights use absolute Zulu time for safety checkpoints. Translating boundaries into local UTC+3:30 is only required for local airport slot allocations and arrival schedules.

FAQ

Zulu to IRST — Frequently Asked Questions

What is IRST and its offset from Zulu time?

IRST stands for Iran Standard Time. It operates at a permanent standard offset of UTC+3:30 (three hours and thirty minutes ahead of Zulu/UTC time).

How do I convert Zulu time to IRST?

To convert Zulu to IRST, add exactly 3 hours and 30 minutes to the Zulu time. For example, 12:00Z becomes 15:30 IRST. When adding to minutes, remember to carry over the hour if the sum exceeds 60 minutes.

Does Iran observe Daylight Saving Time (DST)?

No. Iran officially abolished daylight saving time in September 2022. IRST remains at UTC+3:30 year-round, without shifting in the summer.

Why does Iran use a half-hour (+30 mins) offset?

Iran uses a UTC+3:30 offset to align solar noon with the central meridian of the country. This provides a more natural daylight alignment across its territory than adopting a whole-hour zone.

When does the calendar date rollover to the next day in IRST?

The local day in Iran rolls over to the next calendar date when Zulu time reaches 20:30Z. Any Zulu timestamp at or after 20:30Z represents the next calendar day locally in Tehran (00:00 IRST).

Why do trans-continental flights use Zulu instead of IRST over Tehran FIR?

Because high-altitude flights cross boundaries rapidly, coordinating slots and handovers in local fractional times like UTC+3:30 increases the risk of timing errors. Absolute Zulu time serves as the unified standard for regional controllers and pilots.

How do I coordinate slots at Tehran Imam Khomeini Airport?

Flight plan filing, slot allocations, and active cockpit logs must utilize Zulu time. Local IRST coordinates passenger ticketing, airport ground crews, and public schedules.

What is the international IANA time zone database identifier for IRST?

In the IANA time zone database, Iran is represented by the zone identifier Asia/Tehran. Systems utilizing this identifier automatically map standard time to the UTC+3:30 offset year-round following the 2022 reform.

How did the 2022 DST abolishment in Iran affect commercial flight planning?

Before September 2022, airline dispatchers had to adjust local arrival and departure times twice a year. The permanent transition to UTC+3:30 simplified scheduling operations and stabilized slot coordination at international airports like Imam Khomeini (IKA).

Are there other countries that use the UTC+3:30 fractional offset?

No, Iran is currently the only country in the world that observes the UTC+3:30 offset. This unique choice makes careful coordination essential for international systems.