This is a job for Julian day numbers.
Julian day is the continuous count of days since the beginning of the Julian Period and is used primarily by astronomers, and in software for easily calculating elapsed days between two events (e.g. food production date and sell by date).1
The Julian Day Number (JDN) is the integer assigned to a whole solar day in the Julian day count starting from noon Universal time, with Julian day number 0 assigned to the day starting at noon on Monday, January 1, 4713 BC, proleptic Julian calendar (November 24, 4714 BC, in the proleptic Gregorian calendar),23 a date at which three multi-year cycles started (which are: Indiction, Solar, and Lunar cycles) and which preceded any dates in recorded history.[a] For example, the Julian day number for the day starting at 12:00 UT (noon) on January 1, 2000, was 2 451 545.4
The Julian date (JD) of any instant is the Julian day number plus the fraction of a day since the preceding noon in Universal Time. Julian dates are expressed as a Julian day number with a decimal fraction added. For example, the Julian Date for 00:30:00.0 UT January 1, 2013, is 2 456 293.520 833. Expressed as a Julian date, right now it is 2459110.2399306. [refresh]
You want the number of days since October 23, 4004 B.C.
Nobody counted time as so many years or days until January 1, AD 1 back in 4004 BC. As far as I know the calendars which count years BC (or BCE) are the Julian and the Gregorian calendars, created millenia after 4004 BC. Therefore a date given as 4004 BC must be in the proleptic version of one of those calendars.
The adjective proleptic is defined as:
Of a calendar, extrapolated to dates prior to its first adoption; of those used to adjust to or from the Julian calendar or Gregorian calendar.
And I note that October 23, 4004 BC in the proleptic Julian calendar would be a different date than October 23, 4004 BC in the proleptic Gregorian clanedar.
The current Julian date is given as: 2459110.23958.
Thus there is a fair chance that it will still be Julian day 2459110 when you read this. That is September 17, 2020, or Julian day 2,459,110.
You seem to be asking about Archbishop Ussher's date for the Creation, 23 October 4004 BC. His date of 4004 BC for the Creation is hardly the only date which has been proposed.
In 1738, Alphonse Des Vignoles [fr] said he had collected over 200 different estimates, ranging from 3483 BC to 6984 BC.
Anyway, this online calculator says that October 23, 4004 BC was Julian date 259258.29721.
It doesn't specify whether 259258 equals October 23, 4004 BC in the proleptic Julian or Gregorian calendar.
2,459,110 minus 259,258 is 2,199,852 days. So I have found one of the two possible answers to your question.