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Rules","url":"https://www.nist.gov/pml/time-and-frequency-division/popular-links/daylight-saving-time-dst"},{"@type":"CreativeWork","name":"Natural Earth map data","url":"https://www.naturalearthdata.com/about/terms-of-use/"}],"about":{"@id":"https://ptob.dev/#protocol"}}]}],"content":{"mediaType":"text/markdown","headings":[{"level":1,"text":"Local time in a UTC timing mesh","url":"https://ptob.dev/blog/local-time-utc-mesh/#main"},{"level":2,"text":"Local time without configuring every clock","url":"https://ptob.dev/blog/local-time-utc-mesh/#local-time-without-configuring-every-clock"},{"level":2,"text":"UTC stays the foundation","url":"https://ptob.dev/blog/local-time-utc-mesh/#utc-stays-the-foundation"},{"level":2,"text":"A setup that can move with you","url":"https://ptob.dev/blog/local-time-utc-mesh/#a-setup-that-can-move-with-you"},{"level":2,"text":"Explore the details","url":"https://ptob.dev/blog/local-time-utc-mesh/#related-title"},{"level":3,"text":"Why PToB is standardizing on UTC","url":"https://ptob.dev/blog/local-time-utc-mesh/#main"},{"level":3,"text":"Deploying a timing mesh","url":"https://ptob.dev/blog/local-time-utc-mesh/#main"},{"level":2,"text":"Sources and further reading","url":"https://ptob.dev/blog/local-time-utc-mesh/#sources-title"},{"level":2,"text":"Cite this article","url":"https://ptob.dev/blog/local-time-utc-mesh/#cite-title"}],"links":[{"text":"Jonathan Yantis","url":"https://github.com/yantisj2/PToB/blob/main/CREDITS.md"},{"text":"our decision to standardize PToB on UTC","url":"https://ptob.dev/blog/why-utc/"},{"text":"regional calendars","url":"https://www.iana.org/time-zones"},{"text":"Why PToB is standardizing on UTC The common timebase behind the mesh and its client interfaces.","url":"https://ptob.dev/blog/why-utc/"},{"text":"Deploying a timing mesh How grandmasters, relays and receiving clocks fit together.","url":"https://ptob.dev/deployment/"},{"text":"IANA Time Zone Database","url":"https://www.iana.org/time-zones"},{"text":"NIST Daylight Saving Time Rules","url":"https://www.nist.gov/pml/time-and-frequency-division/popular-links/daylight-saving-time-dst"},{"text":"Natural Earth map data","url":"https://www.naturalearthdata.com/about/terms-of-use/"},{"text":"https://ptob.dev/blog/local-time-utc-mesh/","url":"https://ptob.dev/blog/local-time-utc-mesh/"},{"text":"Back to the blog","url":"https://ptob.dev/blog/"},{"text":"Inspect the project evidence","url":"https://github.com/yantisj2/PToB/blob/main/evidence/README.md"}],"text":"# Local time in a UTC timing mesh\n\nPower up a time mesh wherever you need one. Give people the local time they expect and devices the shared UTC reference they need.\n\n[Jonathan Yantis](https://github.com/yantisj2/PToB/blob/main/CREDITS.md) 29 October 2026  3 min read\n\n![GNSS position and a DST calendar select Chicago at a grandmaster showing 13:00 UTC. Its BLE broadcast carries the zone and UTC minus five-hour offset to three clients showing 08:00 CDT, above an uninterrupted UTC timeline.](https://ptob.dev/blog/local-time-utc-mesh-v1.png)\n\nConcept illustration. The grandmaster selects the zone and current seasonal offset; clients apply that offset for local display while UTC remains the shared timebase. Clock readings are illustrative.\n\nIn this post\n\nOur aim is an instant precision time mesh: bring the reference, power up your clients, and let the network share time. A workshop, a temporary lab or a field installation should be able to use the same straightforward setup. Once the grandmaster has a valid reference, clocks and sensors can join it without each needing their own GNSS receiver or Internet time service.\n\nLocal timezone support makes that experience more useful. The clock on the wall should show the hour people expect, while the instruments beside it record events against one shared UTC reference. Moving the installation or crossing a daylight saving boundary should not turn into a round of clock configuration.\n\n## Local time without configuring every clock\n\nA precision mesh can put a common time reference within reach of small, inexpensive devices. To make it convenient in everyday use, we also need to take care of the ordinary clock-setting work: choosing a region, applying its offset and following its seasonal changes.\n\nPToB will put those decisions at the grandmaster. Its GNSS position will select a supported region from a compact geographic database, and that region’s calendar will supply the current UTC offset. The grandmaster will distribute the result over Bluetooth; clients and relays will inherit it through the mesh.\n\nThat means one local-time policy for the installation. A new clock can receive the same setting as the clocks already around it. Receivers will need neither a geographic database nor an Internet lookup, keeping the work small enough for simple microcontrollers.\n\n## UTC stays the foundation\n\nTimezone support builds on [our decision to standardize PToB on UTC](https://ptob.dev/blog/why-utc/). In that article, we discussed International Atomic Time (TAI), the Precision Time Protocol (PTP), and why supplying UTC directly makes life simpler for small clients. TAI conversion and PTP interoperability belong at the interfaces that need them, with the appropriate time properties.\n\nLocal time follows the same principle: apply the conversion where it is needed. Clock faces will add the regional offset for display. Event timestamps, precision timing, PPS and USB time output will keep their existing time coordinates. Selecting a timezone will not reset the mesh epoch or change the precision clock model.\n\nThis matters when local time repeats in autumn or skips an hour in spring. Operators can see the familiar local clock change while logs and measurements retain their common UTC reference. We can make the mesh comfortable to use without moving its timing foundation every time the clocks change.\n\n## A setup that can move with you\n\nThe design is intended to travel with the equipment. In regions covered by automatic selection, fresh GNSS positions will establish the local zone. A manual zone will let an installation choose its calendar explicitly, and a fixed offset will serve deployments that need a particular convention. Receivers will follow the serving grandmaster’s zone, including clients physically elsewhere.\n\nThe over-the-air addition is just four bytes: a zone identifier and the current offset in minutes. The [regional calendars](https://www.iana.org/time-zones) stay at the GM. When daylight saving changes the offset, fresh authenticated broadcasts will carry the new value to clients. The precision timing payloads stay unchanged.\n\nAutomatic geography will cover selected regions; manual choices provide the alternative elsewhere. If a usable zone cannot be established, its calendar expires or its radio metadata becomes stale, clock presentation will return to UTC. The shared time reference remains useful even when a local-time setting is unavailable.\n\nThe experience we want is simple: set up a precision time mesh wherever the work takes you, let its clocks show useful local time, and keep every device working from the same UTC base.\n\nEvery timestamp needs a reference.\n**Which event did you capture?**\n\n## Explore the details\n\n[Why PToB is standardizing on UTC The common timebase behind the mesh and its client interfaces.](https://ptob.dev/blog/why-utc/)[Deploying a timing mesh How grandmasters, relays and receiving clocks fit together.](https://ptob.dev/deployment/)\n\n## Sources and further reading\n\nPrimary references for the hardware and methods discussed.\n\n1. [IANA Time Zone Database](https://www.iana.org/time-zones)\n\n   Regional UTC offsets and daylight saving rules, maintained as civil-time policies change.\n2. [NIST Daylight Saving Time Rules](https://www.nist.gov/pml/time-and-frequency-division/popular-links/daylight-saving-time-dst)\n\n   The repeated autumn hour, the spring gap and the separation of UTC distribution from local-time conversion.\n3. [Natural Earth map data](https://www.naturalearthdata.com/about/terms-of-use/)\n\n   Public-domain geographic inputs for the compact regional position lookup.\n\n## Cite this article\n\nJonathan Yantis. Local time in a UTC timing mesh PToB Blog. Published 29 October 2026.\n\nArticle permalink: [https://ptob.dev/blog/local-time-utc-mesh/](https://ptob.dev/blog/local-time-utc-mesh/)\n\n[Back to the blog](https://ptob.dev/blog/)[Inspect the project evidence](https://github.com/yantisj2/PToB/blob/main/evidence/README.md)"}}