eday

The eday package provides functions for converting between dates and epoch days, a concept where dates are represented as the number of days since a reference epoch. This is useful for date arithmetic and conversion.

Installation

Install eday using pip:

pip install eday

Principle

Method signature.

import eday

eday(<datetime.datetime> | '<ISO-STRING>' | '<TIME-STRING>' | <float|int>) # -> Eday <float>

eday.from_jd(<float>) # -> Eday <float>

eday.now() # -> Eday <float>

eday.to_date() # -> datetime.datetime

eday.to_jd() # -> <float> (Julian day)

Usage

The imoprted eday can be called directly, and supports polymorphic creation from diferent types, and simple arithmetic.

import eday

# Create from float
eday(0) # 0.0 <1970-01-01 00:00:00+00:00>

# Passing large numbers displays date representations as well
eday(-2440587.5) # -2440587.5 <-4713-11-24 12:00:0.000000 UTC>

# Create from datetime.datetime
eday(datetime.datetime(1970,1,1))

# Create from ISO dates
eday('1969-12-31 17:00:00-07:00')

# Create from Time string
eday('-7:00') # 7 hours before "epoch 0". NOTE: If '-' is before ISO 8610 string, it means BC (before common era.)

# Unrestricted float numbers of hours, minutes, seconds can be used
eday('100.5:100.15:100.125') # (100.5 hours, 100.15 minutes, 100.125 seconds)

# Create from Julian days:
eday.from_jd(2459580.5) # 18993.0 <2022-01-01T00:00:00+00:00>

# Date arithmetic
eday('2024-10-04') - eday.now()

# Time arithmetic
eday('1:50') - eday('0:10:15.123')  # (1 hour 50 minutes - 10 minutes 15.123 seconds)

# Convert to Julian day
eday('2024-10-04').to_jd() # 2460587.5

# Format as decimal unix day and time, for viewing as date and time string.
eday('2024-10-04 12:15').format() # 20,000 T 5:10:41.6666668

About

The eday package features the Eday class, which represents "epoch days" (Unix seconds in days). It inherits from float, providing conversions to/from datetime, and supports arithmetic operations for quick date calculations.

Main Functions:

1. from_date: Converts a date object or ISO format string to the number of days since the epoch.
2. from_jd: Convets Julian day to number of days since the epoch.
3. now: Returns the current UTC time as a number of days since the epoch.

Auxiliary Functions:

4. to_date: Converts Eday object to datetime.datetime if possible.
5. to_jd: Converts Eday object to Julian day.

Miscellanous Functions:

6. format: Formats Eday as Decimal Unix day and time in a fashion similar to datetime.datetime.isoformat().

However, you can call the imported eday directly (as shown in the examples above) to use it with minimal typing to do time and calendar computations.

Using Epoch Days without this package (Python 2 & Python 3)

If you don't need these extra features, and just need to convert dates to/from edays, you could simply use:

import time, datetime

def d2e(date): # datetime.datetime -> float
    return time.mktime(date.utctimetuple()) / 86400.

def e2d(eday): # datetime.datetime -> float
    return datetime.datetime.utcfromtimestamp(eday * 86400.)

def eday():
    return d2e(datetime.datetime.utcnow())

Using Epoch Days from Terminal

Linux users can use these zsh functions:

function d2e { # isodate -> eday
 local n=$((($(date -u --date="$1" +%s%9N)/864)*1000))
 local day=${n:0:-14}; local hour=${n:(-14)}
 echo $day.${hour} | sed 's/\.\?0*$//'
}

function e2d { # eday -> isodate
 local second=$(printf "%f" $(($1*86400)))
 echo $(date -u +"%Y-%m-%dT%H:%M:%S.%N%:z" -d "@$second")
}

Save these functions in eday.sh and source it or add to /usr/local/bin/eday.

#!/bin/bash
function eday { # eday now
 local n=$((($(date +%s%9N)/864)*1000))
 local day=${n:0:-14}; local hour=${n:(-14)}
 echo $day.${hour:0:${1-11}} # $1: precision
}
eday

Compatibility

The package is compatible with Python 2 (up to version 1.0.1) and Python 3 (from version 1.0.2). Python 2 users will need the dateutil module for parsing ISO format strings.

License

This package is licensed under the MIT License. See the LICENSE file for details.

Contributing

Contributions are welcome! Feel free to open an issue or submit a pull request on GitHub.

GitHub Repository

You can find the source code and contribute to the development of this package on GitHub: https://github.com/mindey/eday

More Information

For more information on epoch days and their applications, you can visit the following link:

• Simple Decimal Calendar