Pinyin: yuán dàn

Meaning: New Year's Day

Sentence: The new calendar called for new year's day to be celebrated jan.1.新歷法規定1月1日慶祝元旦。

More: 

元： 

Pinyin: yuán
Meaning: beginning; first
Radical: 二
Stokes: 4
Traditional: 元
Common words/Phrase:
元旦  [yuán dàn]      【New Years Day】 

元件  [yuán jiàn]      【component element】 

元老   [yuán lǎo]      【senior statesman】

元配  [yuán pèi]       【the first wife】

元兇  [yuán xiōng]     【prime culprit】

旦： 

Pinyin: dàn
Meaning: day
Radical: 日
Stokes: 5
Traditional: 旦
Common words/Phrase:
旦旦    [dàn dàn]          【daily;day by day】 

旦暮   [dàn mù]          【morning and evening-in a short time】

旦日    [dàn rì]           【tomorrow】