Hi! In my network I have 2 Meinberg M200 clocks and 4 other GPS receivers (1 Sure GPS Evaluation board, 2 Garmin 18 LVC and a uBlox EVK-6N). I recorded the GPS timecode strings across 00:00 UTC to see how they would react to the leap second: Sure GPS timecode="$GPGGA,235955.000,4055.2138,N,00829.6016,W,2,7,1.11,267.3,M,51.2,M,0000,0000*4E", timecode="$GPGGA,235956.000,4055.2138,N,00829.6016,W,2,7,1.11,267.3,M,51.2,M,0000,0000*4D", timecode="$GPGGA,235957.000,4055.2138,N,00829.6015,W,2,7,1.11,267.3,M,51.2,M,0000,0000*4F", timecode="$GPGGA,235958.000,4055.2138,N,00829.6015,W,2,7,1.11,267.3,M,51.2,M,0000,0000*40", timecode="$GPGGA,235959.000,4055.2138,N,00829.6015,W,2,7,1.11,267.3,M,51.2,M,0000,0000*41", timecode="$GPGGA,235959.000,4055.2138,N,00829.6015,W,2,7,1.11,267.3,M,51.2,M,0000,0000*41", timecode="$GPGGA,000000.000,4055.2138,N,00829.6015,W,2,7,1.11,267.3,M,51.2,M,0000,0000*40", timecode="$GPGGA,000001.000,4055.2138,N,00829.6015,W,2,7,1.11,267.3,M,51.2,M,0000,0000*41", timecode="$GPGGA,000002.000,4055.2138,N,00829.6015,W,2,7,1.11,267.3,M,51.2,M,0000,0000*42", timecode="$GPGGA,000003.000,4055.2138,N,00829.6015,W,2,6,1.15,267.3,M,51.2,M,0000,0000*46", timecode="$GPGGA,000004.000,4055.2138,N,00829.6015,W,2,6,1.15,267.3,M,51.2,M,0000,0000*41", timecode="$GPGGA,000005.000,4055.2138,N,00829.6015,W,2,7,1.07,267.3,M,51.2,M,0000,0000*42", Meinberg #1 timecode="\x0231.12.16; 6; 23:59:55; +00:00; A ; 40.9204N 8.4936W 343m\x03", timecode="\x0231.12.16; 6; 23:59:56; +00:00; A ; 40.9204N 8.4936W 343m\x03", timecode="\x0231.12.16; 6; 23:59:57; +00:00; A ; 40.9204N 8.4936W 343m\x03", timecode="\x0231.12.16; 6; 23:59:58; +00:00; A ; 40.9204N 8.4936W 343m\x03", timecode="\x0231.12.16; 6; 23:59:59; +00:00; A ; 40.9204N 8.4936W 343m\x03", timecode="\x0231.12.16; 6; 23:59:60; +00:00; L; 40.9204N 8.4936W 343m\x03", timecode="\x0201.01.17; 7; 00:00:00; +00:00; ; 40.9204N 8.4936W 343m\x03", timecode="\x0201.01.17; 7; 00:00:01; +00:00; ; 40.9204N 8.4936W 343m\x03", timecode="\x0201.01.17; 7; 00:00:02; +00:00; ; 40.9204N 8.4936W 343m\x03", timecode="\x0201.01.17; 7; 00:00:03; +00:00; ; 40.9204N 8.4936W 343m\x03", timecode="\x0201.01.17; 7; 00:00:04; +00:00; ; 40.9204N 8.4936W 343m\x03", timecode="\x0201.01.17; 7; 00:00:05; +00:00; ; 40.9204N 8.4936W 343m\x03", Meinberg #2 timecode="\x0231.12.16; 6; 23:59:55; +00:00; A ; 40.9205N 8.4936W 337m\x03", timecode="\x0231.12.16; 6; 23:59:56; +00:00; A ; 40.9205N 8.4936W 337m\x03", timecode="\x0231.12.16; 6; 23:59:57; +00:00; A ; 40.9205N 8.4936W 337m\x03", timecode="\x0231.12.16; 6; 23:59:58; +00:00; A ; 40.9205N 8.4936W 337m\x03", timecode="\x0231.12.16; 6; 23:59:59; +00:00; A ; 40.9205N 8.4936W 337m\x03", timecode="\x0231.12.16; 6; 23:59:60; +00:00; L; 40.9205N 8.4936W 337m\x03", timecode="\x0201.01.17; 7; 00:00:00; +00:00; ; 40.9205N 8.4936W 337m\x03", timecode="\x0201.01.17; 7; 00:00:01; +00:00; ; 40.9205N 8.4936W 337m\x03", timecode="\x0201.01.17; 7; 00:00:02; +00:00; ; 40.9205N 8.4936W 337m\x03", timecode="\x0201.01.17; 7; 00:00:03; +00:00; ; 40.9205N 8.4936W 337m\x03", timecode="\x0201.01.17; 7; 00:00:04; +00:00; ; 40.9205N 8.4936W 337m\x03", timecode="\x0201.01.17; 7; 00:00:05; +00:00; ; 40.9205N 8.4936W 337m\x03", uBlox EVK-6N timecode="$GPGGA,235955.00,4055.21472,N,00829.59411,W,1,07,1.11,251.5,M,49.9,M,,*4F", timecode="$GPGGA,235956.00,4055.21472,N,00829.59416,W,1,07,1.11,251.7,M,49.9,M,,*49", timecode="$GPGGA,235957.00,4055.21472,N,00829.59420,W,1,07,1.11,251.8,M,49.9,M,,*42", timecode="$GPGGA,235958.00,4055.21474,N,00829.59424,W,1,08,1.11,252.1,M,49.9,M,,*4A", timecode="$GPGGA,235959.00,4055.21475,N,00829.59429,W,1,08,1.11,252.3,M,49.9,M,,*45", timecode="$GPGGA,235960.00,4055.21477,N,00829.59433,W,1,08,1.11,252.6,M,49.9,M,,*43", timecode="$GPGGA,235960.00,4055.21477,N,00829.59433,W,1,08,1.11,252.6,M,49.9,M,,*43", timecode="$GPGGA,000001.00,4055.21479,N,00829.59440,W,1,08,1.11,253.0,M,49.9,M,,*44", timecode="$GPGGA,000002.00,4055.21481,N,00829.59443,W,1,08,1.11,253.3,M,49.9,M,,*40", timecode="$GPGGA,000003.00,4055.21482,N,00829.59447,W,1,08,1.11,253.6,M,49.9,M,,*43", timecode="$GPGGA,000004.00,4055.21484,N,00829.59451,W,1,08,1.11,253.8,M,49.9,M,,*4B", timecode="$GPGGA,000005.00,4055.21485,N,00829.59454,W,1,08,1.11,254.1,M,49.9,M,,*40", Garmin 18 LVC #1 timecode="$GPGGA,235955,4055.2362,N,00829.5576,W,2,07,1.2,248.8,M,51.7,M,,*5C", timecode="$GPGGA,235956,4055.2362,N,00829.5576,W,2,07,1.2,248.8,M,51.7,M,,*5F", timecode="$GPGGA,235957,4055.2362,N,00829.5576,W,2,07,1.2,248.5,M,51.7,M,,*53", timecode="$GPGGA,235958,4055.2362,N,00829.5576,W,2,07,1.2,248.5,M,51.7,M,,*5C", timecode="$GPGGA,235959,4055.2362,N,00829.5576,W,2,07,1.2,248.5,M,51.7,M,,*5D", timecode="$GPGGA,235959,4055.2362,N,00829.5576,W,2,07,1.2,248.5,M,51.7,M,,*5D", timecode="$GPGGA,000000,4055.2361,N,00829.5576,W,2,07,1.2,248.4,M,51.7,M,,*5E", timecode="$GPGGA,000001,4055.2361,N,00829.5575,W,2,07,1.2,248.2,M,51.7,M,,*5A", timecode="$GPGGA,000002,4055.2361,N,00829.5575,W,2,07,1.2,248.0,M,51.7,M,,*5B", timecode="$GPGGA,000003,4055.2361,N,00829.5575,W,2,07,1.2,247.9,M,51.7,M,,*5C", timecode="$GPGGA,000004,4055.2360,N,00829.5575,W,2,07,1.2,247.9,M,51.7,M,,*5A", timecode="$GPGGA,000005,4055.2360,N,00829.5575,W,2,07,1.2,247.8,M,51.7,M,,*5A", Garmin 18 LVC #2 timecode="$GPGGA,235955,4055.2222,N,00829.6108,W,1,07,1.4,256.3,M,51.7,M,,*56", timecode="$GPGGA,235956,4055.2222,N,00829.6108,W,1,07,1.4,255.8,M,51.7,M,,*5D", timecode="$GPGGA,235957,4055.2222,N,00829.6108,W,1,07,1.4,255.2,M,51.7,M,,*56", timecode="$GPGGA,235958,4055.2222,N,00829.6108,W,1,06,1.4,254.5,M,51.7,M,,*5E", timecode="$GPGGA,235959,4055.2222,N,00829.6108,W,1,06,1.4,253.8,M,51.7,M,,*55", timecode="$GPGGA,235959,4055.2222,N,00829.6108,W,1,06,1.4,253.8,M,51.7,M,,*55", timecode="$GPGGA,000000,4055.2222,N,00829.6108,W,1,06,1.4,252.5,M,51.7,M,,*58", timecode="$GPGGA,000001,4055.2222,N,00829.6108,W,1,06,1.4,251.8,M,51.7,M,,*57", timecode="$GPGGA,000002,4055.2222,N,00829.6108,W,1,06,1.4,251.2,M,51.7,M,,*5E", timecode="$GPGGA,000003,4055.2222,N,00829.6108,W,1,06,1.4,250.5,M,51.7,M,,*59", timecode="$GPGGA,000004,4055.2222,N,00829.6108,W,1,06,1.4,249.9,M,51.7,M,,*5A", timecode="$GPGGA,000005,4055.2222,N,00829.6108,W,1,06,1.4,249.3,M,51.7,M,,*51", Apparently only the Meinbergs do it properly. The uBlox repeats the 60 second mark twice. Quite odd. I found two servers that weren't ready for the leap second $ date; ntpq -p 192.168.0.129 Sun Jan 1 00:08:46 WET 2017 remote refid st t when poll reach delay offset jitter ============================================================================== +192.168.0.5 .GPS. 1 u 19 64 377 1.418 0.005 0.044 *192.168.0.98 .GPS. 1 u 11 64 377 1.369 -0.017 0.062 -192.168.0.99 .GPS. 1 u 66 64 377 1.381 0.006 15.381 -192.168.0.100 .GPS. 1 u 32 64 377 1.411 0.060 0.037 +192.168.0.101 .GPS. 1 u 28 64 377 1.414 0.001 0.020 +192.168.0.102 .GPS. 1 u 58 64 377 1.312 -0.020 0.060 -62.XX.YYY.65 172.20.9.1 2 u 47 64 377 8.586 1000.61 0.394 62.XX.YYY.66 172.20.9.1 2 u 66 64 377 8.756 1000.84 0.097 $ date; ntpq -p 192.168.0.129 Sun Jan 1 00:09:18 WET 2017 remote refid st t when poll reach delay offset jitter ============================================================================== +192.168.0.5 .GPS. 1 u 51 64 377 1.418 0.005 0.044 *192.168.0.98 .GPS. 1 u 43 64 377 1.369 -0.017 0.062 -192.168.0.99 .GPS. 1 u 31 64 377 1.380 -0.018 0.056 -192.168.0.100 .GPS. 1 u 64 64 377 1.411 0.060 0.037 +192.168.0.101 .GPS. 1 u 60 64 377 1.414 0.001 0.020 +192.168.0.102 .GPS. 1 u 26 64 377 1.312 -0.020 0.066 -62.XX.YYY.65 172.20.9.1 2 u 13 64 377 8.586 1000.61 0.361 62.XX.YYY.66 172.20.9.1 2 u 31 64 377 8.756 1000.84 0.098 $ date; ntpq -p 192.168.0.129 Sun Jan 1 00:12:30 WET 2017 remote refid st t when poll reach delay offset jitter ============================================================================== -192.168.0.5 .GPS. 1 u 45 64 377 1.563 0.064 0.026 -192.168.0.98 .GPS. 1 u 38 64 377 1.478 0.072 0.051 +192.168.0.99 .GPS. 1 u 23 64 377 1.380 -0.018 0.057 *192.168.0.100 .GPS. 1 u 61 64 377 1.379 -0.016 0.065 +192.168.0.101 .GPS. 1 u 55 64 377 1.414 0.001 0.031 -192.168.0.102 .GPS. 1 u 22 64 377 1.425 0.070 0.029 -62.XX.YYY.65 172.20.9.1 2 u 13 64 377 8.658 1000.66 0.362 -62.XX.YYY.66 172.20.9.1 2 u 25 64 377 8.756 1000.84 0.115 But that was to be expected $ ntpq -c rv 62.XX.YYY.65 associd=0 status=0600 leap_none, sync_ntp, no events, unspecified, system="cisco", leap=00, stratum=2, rootdelay=2.380, rootdispersion=0.030, peer=57094, refid=172.20.9.1, reftime=dc138abf.45927e50 Sun, Jan 1 2017 14:03:43.271, poll=10, clock=dc138cb1.5c6d58da Sun, Jan 1 2017 14:12:01.361, phase=0.024, freq=175.72, error=0.02 Cheers, Miguel