> The **average link strength**, a quantity we've computed and put [here](https://github.com/johncarlosbaez/el-nino/blob/master/R/average-link-strength.txt). This file has the average link strength, called $S$, at 10-day intervals starting from day 730 and going until day 12040, where day 1 is the first of January 1948. (For an explanation of how this was computed, see [Part 4](http://johncarlosbaez.wordpress.com/2014/07/08/el-nino-project-part-4/) of the El Niño Project series.)

I think I am confused by the above definition. What is the date of first and last day for which data actually appears in the average-link-strength.txt file?