Off-by-One in lunar date calculation

[benzammour]

Hello,

I encountered an issue with the following code:

carbon.Parse("2021-06-14").Lunar()

carbon version: v1.4.6

golang version: go version go1.16.6 linux/amd64

I expected to get (in yyyy-mm-dd format):

2021-05-05

But I actually get:

2021-05-04

Thanks!

---

Additional info:
I encountered this issue when I was working on a test for a pull request.
The festival tests in calendar.lunar_test.go:52 always fail because the date is off-by-one, causing the program to find empty festivals for a correct date.
I tried fixing the issue myself but I'm simply not versed enough in Chinese dates to do so.

Here's also an example illustrating this error while using the library itself (opposed to the testing environment)

package main

import (
	"fmt"
    "github.com/golang-module/carbon"
)

func main() {
	lunarTime := carbon.Parse("2021-02-12")
	fmt.Printf("First Festival, Greogorian Date: %s\n", lunarTime)

	lunarDate := lunarTime.Lunar()
	festival := lunarDate.Festival()
	fmt.Printf("First Festival, Lunar Date: %d-%d-%d\n", lunarDate.Year(), lunarDate.Month(), lunarDate.Day())
	fmt.Printf("Festival: %s\n", festival)

	fmt.Println()

	lunarTime = carbon.Parse("2021-06-14")
	fmt.Printf("Second Festival, Greogorian Date: %s\n", lunarTime)

	lunarDate = lunarTime.Lunar()
	festival = lunarDate.Festival()
	fmt.Printf("Second Festival, Lunar Date: %d-%d-%d\n", lunarDate.Year(), lunarDate.Month(), lunarDate.Day())
	fmt.Printf("Festival: %s\n", festival)
}

Command:

$ go run main.go 

Output:

First Festival, Greogorian Date: 2021-02-12 00:00:00
First Festival, Lunar Date: 2021-1-1
Festival: 春节

Second Festival, Greogorian Date: 2021-06-14 00:00:00
Second Festival, Lunar Date: 2021-5-4
Festival: 

[gouguoyin]

What is your current time zone？you can try
carbon.Parse("2021-06-14", carbon.PRC).Lunar()

[benzammour]

I'm currently in the time zone of Berlin (GMT+02:00), but using PRC, Berlin or Tokyo does not change the result [1].
The same happens if I use carbon.SetTimezone(carbon.{Berlin, Tokyo, PRC}).Parse("2021-06-14").Lunar().

However, I tried London as well, just to see if it changes anything, and here it converts it correctly [2].

[1]:

func main() {
	lunarDate := carbon.Parse("2021-06-14", carbon.{Berlin, Tokyo, PRC}).Lunar()
	festival := lunarDate.Festival()

	fmt.Printf("Lunar Date: %d-%d-%d\n", lunarDate.Year(), lunarDate.Month(), lunarDate.Day())
	fmt.Printf("Festival: %s\n", festival)
}

Output:

Lunar Date: 2021-5-4
Festival: 

[2]:

func main() {
	lunarDate := carbon.Parse("2021-06-14", carbon.London).Lunar()
	festival := lunarDate.Festival()

	fmt.Printf("Lunar Date: %d-%d-%d\n", lunarDate.Year(), lunarDate.Month(), lunarDate.Day())
	fmt.Printf("Festival: %s\n", festival)
}

Output:

Lunar Date: 2021-5-5
Festival: 端午节

[gouguoyin]

Thank you very much.I found the reason for the bug because CreateFromDateTime() method on line 62 of calendar.lunar.go file didn't set PRC time zone.I will fix this bug in the next version.

[gouguoyin]

Fixed in v1.5.0