well here are some best free tool for twitter marketing needs
HootSuite:https://hootsuite.com/plans/free
you choose the publishing date and time.add attachment and set location and schedule your twit using hootsuite.
Tweroid:http://www.tweriod.com/
Gives you hourly graphs of when your followers are online the most during a 24 hour cycle. It also gives you separate graphs for weekends, Sundays, Mondays and weekdays.
Klout:http://klout.com/
Apart from creating and scheduling tweets, you can measure your twitter profile performance with a special Klout score over a period of time. graph.
FollowerWonk:https://followerwonk.com/
Research Twitter influencers in any niche