Reference implementation of the Network Earth Position Protocol (NEPP), a real-valued calendar and synchronization protocol based on Earth's orbital position.
NEPP represents an Earth Date as ED = Earth Year + apparent solar longitude / 360 degrees and exchanges it using an NTP-inspired UDP protocol. This
repository now contains a V2-only experimental server implementing the
160-octet proposal in draft-iwata-nepp-03.md.
The Python nepp-client remains V1-only. The local iOS 0.0.2 app supports V2;
the already distributed 0.0.1 app cannot query this server.
This is experimental software and an evolving protocol draft. It must not be used as a civil-time source or for safety-critical synchronization. No UDP port has been assigned by IANA; the tools use a configurable private port.
This is a local prototype, not a production cutover. Do not restart an existing V1 deployment with this version until beta clients have been updated. Independent astronomical validation and error bounds are still pending; both coordinates are explicitly reported as accuracy unassessed, never zero error.
Python 3.9 or newer is required.
python -m venv .venv
. .venv/bin/activate
python -m pip install -e '.[astronomy]'
nepp-server --host 127.0.0.1 --port 56377In another terminal:
python -m nepp.probe 127.0.0.1 --port 56377The probe reports coordinates at server transmit time, not network-delay-corrected
local time. It is not a full synchronization client. nepp-client remains V1-only.
The astronomical extra supplies Astropy/ERFA. The provisional model uses epv00,
iterated light time, pure Lorentz aberration, IAU 2006/2000A precession/nutation,
and UT1/GAST for Greenwich solar phase. Its supported interval is 1900–2100.
IERS retrieval runs outside request handling; missing/out-of-range EOP makes SP
unavailable without suppressing ED. --offline uses bundled IERS data only.
Source publication age is unknown; cache refreshes do not invent publication dates.
The server requests no GPS location. The iOS client can optionally use location
on-device to calculate local phase; it never sends location to the server.
Snapshots refresh every 60 seconds, have a 300-second intended extrapolation
interval, and expire completely after --max-age (default 3600 seconds).
Failed/expired refreshes become unassessed holdover; a detected host-clock step
over one second suppresses the snapshot until refreshed. These are operational
limits, not certified accuracy bounds. The host clock remains an experimental input.
python -m unittest discover -s tests -vThe suite covers timestamp boundaries, packet layout and validation, request/response behavior, token/origin verification, bounded cache/holdover, silent V1 rejection, and a UDP loopback exchange. Optional astronomy tests use bundled historical EOP without network access; they are sanity checks, not independent astronomical accuracy certification.
The production entry point defaults to dual-stack UDP port 56377. It caches
the expensive astronomical calculation, interpolates responses from that state,
limits requests per source address, logs lifecycle statistics, and exits cleanly
on SIGINT or SIGTERM.
See the Lightsail and systemd deployment guide for the hardened service unit, firewall configuration, verification, and updates.
src/nepp/ timestamp, packet, clock, server, and client
spec/ protocol draft
tests/ unit and interoperability tests
ios/ SwiftUI client and shared Swift NEPP codec
deploy/ systemd unit and public-server operations guide
webdocs/ Japanese and English source for nepp.kenic.jp
mkdocs.yml documentation-site configuration
The initial iOS client receives NEPP while it is in the
foreground and presents the current coordinate as today: 2026.0457.
BSD 3-Clause. See LICENSE.