re = /^:\d?\d{3}\s[AP]M\s(?:HST|AKDT|[PCEM]DT)\s[A-Z]{3}\s[A-Z]{3}\s\d?\d\s\d{4}$/
str = ':530 PM PDT THU APR 16 2015'
# Print the match result
str.scan(re) do |match|
puts match.to_s
end
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Ruby, please visit: http://ruby-doc.org/core-2.2.0/Regexp.html