As far as the timezone file is concerned, it's two changes but one shift. This is covered more fully in the complete news blob rather than the snippet shown at

As far as the timezone file is concerned, it's two changes but one shift. This is covered more fully in the complete news blob rather than the snippet shown at the top. Today, British Columbia moved from Pacific Standard Time (UTC-8) to Pacific Daylight Time (UTC-7); tomorrow the timezone is renamed to Pacific Time. Unfortunately, the "PT" abbreviation is too short for the timezone database, so while they decide on another form they will temporarily use a bare -7 offset.