From: Luuk <luuk.vosslamber@gmail.com>
Subject: Re: Timestamp alculation identical to Microsoft Excel results
To: pgsql-sql@lists.postgresql.org
Newsgroups: lists.pgsql.sql
References: <xs4all.001c01d36f42$114e5fb0$33eb1f10$@1nar.com.tr>
Message-ID: <20758a7c-051b-276f-3c9b-e106ab3f15ad@invalid.lan>
Date: Thu, 7 Dec 2017 18:27:59 +0100
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101
 Thunderbird/52.5.0
MIME-Version: 1.0
In-Reply-To: <xs4all.001c01d36f42$114e5fb0$33eb1f10$@1nar.com.tr>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Precedence: bulk

On 07-12-17 10:59, Ertan Küçükoğlu wrote:
> Hello,
> 
> There is this Excel report which will be produced by an application. In
> Excel, there is below equation
> 31/10/2017 15:05 - 31/10/2017 14:36:00 = 0:28:21
> 2017-10-31 13:22:17 - 2017-11-01 14:47:45 = 1/1/1900 01:25
> 
> That is very simple in PostgreSQL. Simply subtract two timestamp without
> time zone fields and you have the result. However, Excel also represent that
> result 0:28:21 as double notation 0.0196874999965075 and 1/1/1900 01:25 as
> 1,05935185185081.
> 
> I could not see any way to have same values using PostgreSQL query. I tried:
> extract(epoch from time_field2) - extract(epoch from time_field1) and result
> is 1701 and 5128 respectively.
> 
> Putting aside reasons as to why numbers are used instead of more human
> understandable time format, I would like to learn if having same results as
> Excel is possible.
> 
> Thanks & regards,
> Ertan Küçükoğlu
> 

This is what the maker of excel has to say about that:
https://support.microsoft.com/en-us/help/214094/how-to-use-dates-and-times-in-excel