Liǎng guó qiānshǔ xiéyì, biāozhì zhe hézuò de xīnjìyuán.
The two countries signed an agreement, marking a new epoch of cooperation.
Tips
usage
新纪元 as a capitalized proper noun refers to the New Age spiritual movement 新纪元运动. In lowercase usage, 新纪元 simply means 'a new era' - a fresh epoch in history or development.