MySQL data to Postgres every X time
You'll need to either use an ETL Tool eg Microsoft SSIS. There's plenty of open source products available too. Or you can build your own extract utility using a programming language like PHP, .Net etc. 

The Kimball guys have an article on whether you should build your own or use an off the shelf product.
http://www.kimballgroup.com/2008/04/should-you-use-an-etl-tool/

To schedule the load, you can use windows scheduler on Windows or cron jobs on Unix.