Generated by SassMeister.com.

SassMeister-input-HTML.html

<div class="time"></div>

SassMeister-input.scss

// ----
// Sass (v3.4.14)
// Compass (v1.0.3)
// ----

$times-string: "";

@for $hour from 1 through 23 {
  $times-string: "#{$times-string}#{if($hour < 10, "0#{$hour}", $hour)}:00";
}

@keyframes clock {
  @for $i from 0 to 23 {
    #{$i * 4.166666667}% {
      text-indent: $i * 5 * -1ch;
    }
  }
}

.time::before {
  content: $times-string;
  width: 90px;
  height: 35px;
  display: block;
  overflow: hidden;
  font-family: monospace;
  font-size: 30px;
  text-indent: 0;
  color: #fff;
  background: #000;
  animation-name: clock;
  animation-duration: 4s;
  animation-timing-function: steps(1, start);
}

SassMeister-output.css

@keyframes clock {
  0% {
    text-indent: 0ch;
  }
  4.16667% {
    text-indent: -5ch;
  }
  8.33333% {
    text-indent: -10ch;
  }
  12.5% {
    text-indent: -15ch;
  }
  16.66667% {
    text-indent: -20ch;
  }
  20.83333% {
    text-indent: -25ch;
  }
  25.0% {
    text-indent: -30ch;
  }
  29.16667% {
    text-indent: -35ch;
  }
  33.33333% {
    text-indent: -40ch;
  }
  37.5% {
    text-indent: -45ch;
  }
  41.66667% {
    text-indent: -50ch;
  }
  45.83333% {
    text-indent: -55ch;
  }
  50.0% {
    text-indent: -60ch;
  }
  54.16667% {
    text-indent: -65ch;
  }
  58.33333% {
    text-indent: -70ch;
  }
  62.5% {
    text-indent: -75ch;
  }
  66.66667% {
    text-indent: -80ch;
  }
  70.83333% {
    text-indent: -85ch;
  }
  75.0% {
    text-indent: -90ch;
  }
  79.16667% {
    text-indent: -95ch;
  }
  83.33333% {
    text-indent: -100ch;
  }
  87.5% {
    text-indent: -105ch;
  }
  91.66667% {
    text-indent: -110ch;
  }
}
.time::before {
  content: "01:0002:0003:0004:0005:0006:0007:0008:0009:0010:0011:0012:0013:0014:0015:0016:0017:0018:0019:0020:0021:0022:0023:00";
  width: 90px;
  height: 35px;
  display: block;
  overflow: hidden;
  font-family: monospace;
  font-size: 30px;
  text-indent: 0;
  color: #fff;
  background: #000;
  animation-name: clock;
  animation-duration: 4s;
  animation-timing-function: steps(1, start);
}

SassMeister-rendered.html

<div class="time"></div>