What does it take to keep the world in sync?

Last week, the historic grounds of the Pavillon de Breteuil in Sèvres, France, hosted the 2025 BIPM Summer School (9–11 September). Organized by the BIPM Time Department, the three-day programme offered a rare opportunity for participants to train directly with those responsible for the coordination of Coordinated Universal Time (UTC).

Following the success of the recent BIPM–SIM Summer School in Mexico, and previous initiatives hosted with EURAMET and APMP, this session brought the learning experience back to the BIPM itself—where data gathered from time laboratories around the world are coordinated, and UTC is calculated each month.

Why It Matters

Accurate, reliable timekeeping is the invisible foundation of our connected world. From GNSS navigation and telecommunications, to power grids and high-frequency trading, every second counts.

The BIPM Summer School was designed to equip early-career metrologists, secondees and technical experts with the knowledge and tools they need to support their institutes’ contributions to UTC(k).

The programme blended tutorials, live demonstrations and hands-on analysis using the BIPM’s CBKT training tools. Across the three days, participants explored:

• Day 1 – UTC and UTC(k): Foundations of UTC, its computation, and traceability.
• Day 2 – GNSS: Clock comparisons, GNSS calibration, and practical demonstrations.
• Day 3 – Data Analysis: From timescale algorithms to Python-based Allan tools and topical discussions on the future of optical timescales.

Caption: Participants in hands-on training sessions at the BIPM UTC Summer School 9–11 September 2025, held at BIPM HQ in Sèvres | Photo credit: BIPM

More Than a Course

The technical training was robust, but the value extended well beyond the classroom. Over shared meals, networking sessions and collaborative projects, participants built a global community of practice—one that strengthens ties across regions and fosters the next generation of experts in time and frequency metrology.

1. "The programme was highly practical, offering valuable hands-on experience and insights rarely found in textbooks. As someone new to in world of UTC, I found it to be an excellent platform for learning, exchange, networking, and collaboration — an experience that will certainly benefit me going forward, with the added bonus of amazing food too." - Aniket Hendre, SKAO, United Kingdom 
    
2. "I am very grateful to the BIPM for organising the BIPM UTC Summer School, which provided the opportunity to learn directly from world-leading experts and national metrology institutes, as well as to exchange ideas with fellow participants. I am truly motivated to apply what I have learned to benefit both my institute and my country." - Thayathip Thongtan, National Institute of Metrology Thailand, NIMT 

Caption: Group photo of participants from the BIPM UTC Summer School 9–11 September 2025, held at BIPM HQ in Sèvres | Photo credit: BIPM

Looking Ahead

The BIPM Summer School in Sèvres took place at a pivotal moment. With preparations underway for the redefinition of the SI second, initiatives like this are helping ensure that national laboratories worldwide are ready to participate in, and benefit from, the next era of timekeeping.

As the BIPM continues its 150th anniversary year, the Summer School stands as a reminder of its enduring mission: enabling all countries to contribute meaningfully to the international system of measurement.

Related Video

Why does the redefinition of the second matter—and what steps are underway to prepare for it?

Watch this recent BIPM150 interview with Nobel Laureate William D. Phillips: https://youtu.be/QMNx5LU54EI