`encoding/cbor` does not correctly encode or decode a `time.Time` with `epoch` tag

[BigBoyBarney]

Hi!

Context

When encoding time.Time fields with specific values as cbor and then parsing it, a Bad_Tag_Value error is raised.

• Operating System & Odin Version: Linux - odin version dev-2025-10
• Please paste odin report output:
  Odin: dev-2025-10
  OS: Debian GNU/Linux forky/sid, Linux 6.16.8-200.fc42.x86_64
  CPU: AMD Ryzen 7 5800X3D 8-Core Processor
  RAM: 32004 MiB
  Backend: LLVM 19.1.7

Expected Behavior

Encoding and decoding a time.Time field always works.

Reproduction:

If the value of the time field is less than 1e11 nanoseconds (empirical), it fails.

Test :: struct {
    time: time.Time `cbor_tag:"epoch"`,
}

main :: proc() {
	// via type declaration
	Error_Implicit: {
		test: Test
		encoded, marshal_err := cbor.marshal_into_bytes(test)
		if marshal_err != nil { fmt.printfln("%#v", "Marshal error") }

		decoded_test: Test
		decode_err := cbor.unmarshal_from_bytes(encoded[:], &decoded_test)
		fmt.printfln("%#v", decode_err) // Bad_Tag_Value
	}

	// via direct initialisation
	Error_Explicit: {
		test := Test{}

		encoded, marshal_err := cbor.marshal_into_bytes(test)
		if marshal_err != nil { fmt.printfln("%#v", "Marshal error") }

		decoded_test: Test
		decode_err := cbor.unmarshal_from_bytes(encoded[:], &decoded_test)
		fmt.printfln("%#v", decode_err) // Bad_Tag_Value
	}

	// via time.from_nanoseconds(0)
	Error_Time_Unix_0: {
		test := Test{time.from_nanoseconds(0)}

		encoded, marshal_err := cbor.marshal_into_bytes(test)
		if marshal_err != nil { fmt.printfln("%#v", "Marshal error") }

		decoded_test: Test
		decode_err := cbor.unmarshal_from_bytes(encoded[:], &decoded_test)
		fmt.printfln("%#v", decode_err) // Bad_Tag_Value
	}

	// via time.from_nanoseconds(1e11)
	Success_Time_Unix_1e11: {
		test := Test{time.from_nanoseconds(1e11)} // 1e10 still throws an error

		encoded, marshal_err := cbor.marshal_into_bytes(test)
		if marshal_err != nil { fmt.printfln("%#v", "Marshal error") }

		decoded_test: Test
		decode_err := cbor.unmarshal_from_bytes(encoded[:], &decoded_test)
		fmt.printfln("%#v", decode_err) // nil => Works as expected
	}

	// via time.now()
	Success_Time_Unix_Now: {
		test := Test{time.now()}

		encoded, marshal_err := cbor.marshal_into_bytes(test)
		if marshal_err != nil { fmt.printfln("%#v", "Marshal error") }

		decoded_test: Test
		decode_err := cbor.unmarshal_from_bytes(encoded[:], &decoded_test)
		fmt.printfln("%#v", decode_err) // nil => Works as expected
	}
}

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Cheers!
Barney

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Aparte: I love Odin!