filter5

awk -F'~' -v col="$DATE_COL" -v cutoff="$CUTOFF" '
function month2num(m) {
    return (index("JanFebMarAprMayJunJulAugSepOctNovDec", m) + 2)/3
}
{
    if (NF < col) { print; next }
    d = $col
    gsub(/:[0-9]{3}[APMapm]/, substr(d, match(d, /:[0-9]{3}/)+1), d)   # drop ms
    match(d, /^([A-Za-z]{3})[[:space:]]+([0-9]{1,2})[[:space:]]+([0-9]{4})[[:space:]]+([0-9]{1,2}):([0-9]{2}):([0-9]{2})[[:space:]]+(AM|PM)/, a)
    if (!a[0]) next
    mon = month2num(toupper(a[1]))
    mday = a[2]+0; year = a[3]+0
    hour = a[4]+0; min = a[5]+0; sec = a[6]+0
    ampm = a[7]
    if (ampm == "PM" && hour < 12) hour += 12
    if (ampm == "AM" && hour == 12) hour = 0
    ts = mktime(year " " mon " " mday " " hour " " min " " sec)
    if (ts >= cutoff) print
}'