How does Daylight Saving Time work in Paraguay?

My memory may be a bit foggy, and my Spanish comprehension was not excellent, but I will recall my experience as best I can. Maybe someone can shed some light on my confusion.

Begin from the United States, I am familiar with Daylight Saving Time, elsewhere known as Summer Time. I lived in Asunción, Paraguay, for a year in 2012-2013, where I managed the computers for a small non-profit organization. I arrived there in Southern Hemisphere winter. One day in the spring, I got to work and found that I was an hour late because the clocks had been set forward for "hora verano" (summer time). This was a surprise, but it made sense to me. I noticed that the computers had not observed the shift, even though their Windows time zone setting was "Paraguay." I reasoned that Microsoft had neglected to include Paraguayan summer time in its settings, and I manually set all the computer clocks forward.

A few weeks later, all the computer clocks shifted forward an hour. When I asked why, it was explained to me that while this was the official starting date for summer time, the government had declared that it would start a few weeks earlier than the official date. Also, they do this every year.

Maybe I misunderstood something, but if the government doesn't like the official start date for summer time, why don't they change it?