ACT - Registration and test information at https://www.act.org/
Usually given 7 times a year: September, October, December, February, April, June, and July. Deadlines are typically 5-6 weeks prior to the test dates. (ACT) Sending your scores
SAT - Registration and test information at https://www.collegeboard.org/
Given 7 times a year: March, May, June, August, October, November, and December. Deadlines are typically 4-5 weeks prior to the test dates. (SAT) Sending your scores
Test Optional - What It Means and Things to Consider
The pandemic has changed the landscape of standardized testing in college admissions.  Many institutions have opted to go test-optional or test-blind.  Research the standardized testing policy at the institutions to which you wish to apply.  See the link above for more information on what it means to be test optional. 
If you would like to submit test scores, or are applying to an institution that requires them, know that the majority of four-year colleges require students to take at least one of these exams by December of their senior years. NOTE: October is the last test date that makes scores available in time for early decision and early action programs.   
* Recommendation: juniors taking the tests should plan to do so in the spring, or by the end of their junior years, so they can re-take the tests, if needed, in the fall.   
California State University (CSU) testing policy (as of March 2022):
CSU will not consider SAT or ACT test scores when making admissions decisions or awarding scholarships. Please click here for more information
Press release announcing the final decision to adopt test-free admission - (3/23/22)
University of California (UC) testing policy (as of November 2021):
UC will not consider SAT or ACT test scores when making admissions decisions or awarding scholarships. Please click here for more information
"UC slams door on standardized admissions tests" - LA Times (November 2021)