SELECT
     T.CDate AS NewDate,
     T.MaxVal,
     T.CurName
FROM (
    SELECT
        MAX(CR.CurrencyValue) - MIN(CR.CurrencyValue) AS MaxVal,
        CR.CurrencyName AS CurName,
        CAST(YEAR(CR.Date) AS nvarchar) + N'.' + CAST(MONTH(CR.Date) AS nvarchar) AS CDate
    FROM Currencies CR
    GROUP BY YEAR(CR.Date), MONTH(CR.Date), CR.CurrencyName) AS T
WHERE T.MaxVal IN (
    SELECT
        MAX(T1.MaxVal)
    FROM (
        SELECT
            MAX(CR1.CurrencyValue) - MIN(CR1.CurrencyValue) AS MaxVal,
            CR1.CurrencyName AS CurName,
            CAST(YEAR(CR1.Date) AS nvarchar) + N'.' + CAST(MONTH(CR1.Date) AS nvarchar) AS CDate
        FROM Currencies AS CR1
        GROUP BY YEAR(CR1.Date), MONTH(CR1.Date), CR1.CurrencyName) as T1
    GROUP BY T1.CurName)