And `date` returns a timestamp with seconds precision. `time sh -c 'if [ "$(date)" != "Sat Oct 31 16:00:00 EDT 2015" ]; then sleep 1; fi'` took around 1.010 se

And `date` returns a timestamp with seconds precision. `time sh -c 'if [ "$(date)" != "Sat Oct 31 16:00:00 EDT 2015" ]; then sleep 1; fi'` took around 1.010 seconds on my machine, but that includes starting a new shell, so there's probably a much smaller than 1% chance that that particular second will be missed. EDIT: here's a little program to test this: #!/usr/bin/env bash while true; do target=$(expr $(date +%s) + 2) while true; do now=$(date +%s) if [ "$now" != "$target" ]; then if [ "$now" -gt "$target" ]; then echo "FAIL :(" break else sleep 1 fi else echo "OK! :)" break fi sleep 0.1 done done Adjust the "sleep 0.1" to increase or decrease the perecentage of failures. Remove to see that it (almost) never fails.