fmtdate from Unix Epoch or Excel Epoch number -- feature request

[avilella]

Would it be possible to implement a date converter in fmtdate from Unix Epoch or Excel Epoch?

See below:

echo -e "date\n1737454964\n1737454954" | csvtk fmtdate -f 1 --unix-epoch

echo -e "date\n45674.412777777776\n45674.410474537035" | csvtk fmtdate -f 1 --excel-epoch

See the explanation the ChatGPT Enterprise gave me for this (in bash):

# Input Excel serial date
excel_date="45677.39685185185"

# Define constants
excel_epoch="1900-01-01"
unix_epoch="1970-01-01"

# Convert Excel date to seconds since the Unix epoch
seconds_since_epoch=$(
  awk -v ed="$excel_date" 'BEGIN {
    excel_epoch_offset = 25569;  # Excel epoch in days since Unix epoch
    seconds_per_day = 86400;
    seconds_since_epoch = (ed - excel_epoch_offset) * seconds_per_day;
    print seconds_since_epoch;
  }'
)

# Format the date in YYYY-MM-DD hh:mm:ss
formatted_date=$(date -u -d "@$seconds_since_epoch" +"%Y-%m-%d %H:%M:%S")

echo "$formatted_date"

[shenwei356]

It seems that the package for parsing date (https://github.com/araddon/dateparse) can support it (UNIX epoch)