using System.Globalization;
using System.Text.RegularExpressions;
public static void Main()
string input = "FX Spots Forwards Summary2_29-Jun-2018.csv";
input = Regex.Replace(input,
"\\S(?<day>\\d{2})-(?<month>\\w{3})-(?<year>\\d{4})\\b",
TimeSpan.FromMilliseconds(150));
Console.WriteLine(output);