Yii2-Date Picker extension not getting installed

In composer.json I entered "nex/yii2-datepicker" : "*" in require section and minimum stability is stable. Now I run composer update, then foll error is displayed

Loading composer repositories with package information

Updating dependencies (including require-dev)

Content-Length mismatch

packagist.org could not be fully loaded, package information was loaded from the local cache and may be out of date

Your requirements could not be resolved to an installable set of packages.

Problem 1

  • The requested package nex/yii2-datepicker * is satisfiable by nex/yii2-datepicker[dev-master] but these conflict with your requirements or minimum-stability