Proposals mainly differ in their selection of a leap rule, placing of the leap item (usually middle or end of the year), in the start day of the week and year, in the number (12 or 13) and size of months and in connected naming; some are compatible to the week date of ISO 8601.
建議的差別主要呈現在置閏的規則、置閏的位置（通常是在一年的中間或是結束）、在一年開始的日期和週日、月的大小和數量（12或13個月）、各月的名稱和連接；有些必須與ISO 8601的周日日期相容。