The Palo Alto, East Palo Alto, Fremont, Mountain View, and Los Gatos-Monte Sereno police departments are participating in this first worldwide event with 160 agencies taking part.
They're tweeting about their service calls to increase awareness about police work and their issues.
Around 11:30 a.m. Fremont police tweeted, "Auto burglary reported on Technology. While out there a warrant service was conducted on a 32 year old male across street. Rita run #poltwt."
The agencies are promoting the use of social media by law enforcement by using the same hashtag: poltwt.