Produces a UT1-UTC (also known as DUT1) graph.

Reads source data from finals.all file. If the file does not exist, downloads it from US Naval Observatory website and saves it on disk. Subsequent runs of the script will reuse the file. To force fetching a new copy, delete finals.all file.

Saves the graph to Leapsecond.ut1-utc.svg file. Overwrites the file if necessary.

Usage

If you’ve downloaded this repository, just execute the script. Otherwise, either clone it or download the script directly like so:

wget https://codeberg.org/mina86/make-ut1-utc-graph/raw/branch/master/make-ut1-utc-graph.py &&
    python make-ut1-utc-graph.py

To regenerate the graph from fresh data delete the finals.all file:

[ -e finals.all ] && rm finals.all
python make-ut1-utc-graph.py

Other version

The script is based on the following procedure:

wget https://maia.usno.navy.mil/ser7/finals.all

cut -c 1-2,3-4,5-6,8-15,58,59-68 --output-delimiter " " \
        finals.all > finals-cut.txt
grep "P" finals-cut.txt > finals-pred.txt
grep "I" finals-cut.txt > finals-iers.txt

cat >leapsecs.gnuplot <<EOF
set xdata time
set timefmt "%Y-%m-%d"
set format x "%Y"
set xrange ["1973-01-01":"2028-01-01"]
set yrange [-0.9:0.9]
set xtics "1970-01-01", 5 years
set mxtics time 1 year
set grid lt 3 lc 0
set terminal svg font "Arial,16"
set style line 1 lc rgb 'dark-green' lt 1
set style line 2 lc rgb 'red' lt 1
unset key
makedate(y,m,d,j) = sprintf("%04d-%02d-%02d", (j <= 51543 ? 1900 + y : 2000 + y), m, d)
set output 'Leapsecond.ut1-utc.svg'
plot \
    'finals-iers.txt' \
        using (makedate($1,$2,$3,$4)):($6) \
        with lines linestyle 1 title 'Measured', \
    'finals-pred.txt' \
        using (makedate($1,$2,$3,$4)):($6) \
        with lines linestyle 2 title 'Predicted'
set output
EOF

gnuplot leapsecs.gnuplot