Obtaining deltaT for use in software I'm currently developing a javascript application in which I want to calculate the approximate position of the sun. This works quite fine but requires the value for deltaT (TT-UT) to be set depending on the year for which I want to calculate the solar position. 

Currently, I'm using a default value of 67 for my calculation. However, since I want to calculate the solar position for several years I'm looking for a convenient way to obtain the deltaT value for each year.

To all of you, that have some experience with programming:
Is there any interface (API) that provides me with the desired values?
Of course, it would also be sufficient to get the universal and terrestrial time so that I can calculate deltaT on my own.
See Where can I find/visualize planets/stars/moons/etc positions? for an extremely general answer on how to compute positions, but the files you're looking for specifically are the "leap second kernels" at http://naif.jpl.nasa.gov/pub/naif/generic_kernels/lsk/

There was a mild kerfuffle on spice-discussion lists when NASA failed to update the kernels after the end-of-2016 leap second was announced, but they have updated it now.