Timestamps Pt 2 – Reducing Storage Size

Automated data-loggers may need to generate thousands if not millions of timestamps per day. If we could reduce the size of the timestamp 50% or more, the memory savings become significant. In the previous post we showed that nearly 15 bits (about 16000 days) can be discarded if we simply measure time relative to a configurable start time T0. More redundant bits can be eliminated if we shorten the amount of time before the clock rolls over. However, this requires that T0 be reset periodically. Here is how storage size affects the maximum time between T0 resets.

  • 2 bytes about 1.1 minutes
  • 3 bytes about 4.66 hours
  • 4 bytes about 49.7 days

Advantages

  • Significant Reduction in Storage Size
  • Well suited for high frequency data logging
  • Subtraction of T0 is not computationally intensive

Disadvantages

  • Without T0; the time is no longer portable
  • Adding T0 doubles the amount of data to be ported.
  • Doesn’t address light speed distance measurement
  • Still requires processing for human readability

Suggested Use Case

Confine usage to data storage and retrieval as in the following example.

store(System.currentTimeMillis()-this.T0, rowData, row);
long then = load(rowData, row) + this.T0;