BIPM - Bureau International de Poids et Mesures

• https://www.bipm.org/en/home
• https://www.bipm.org/kcdb/ (KCDB is the Key Comparison Data Base of the BIPM)
• https://www.bipm.org/en/time-metrology
• https://www.bipm.org/en/time-ftp/

Germany

• Clock - https://uhr.ptb.de/ (including Δt to local device)
• UTC(PTB)
• Metrological services - https://www.ptb.de/cms/en/metrological-services.html

Norway

• Justervesenet (Norwegian Metrology Service): https://www.justervesenet.no/en/ ; https://www.justervesenet.no/maleteknikk/tid-og-frekvens/noyaktig-tid/

Poland

• UTC(PL)
• UTC(AOS)

Serbia

• Clock - https://www.dmdm.rs/en/
• UTC+1 (Belgrade, Serbia)

Switzerland

• UTC(CH)