Hi Samer,
I believe you don't need the comma after the year specification (I tend to believe you put it based on the customary punctuation in English).

I don't know really if the comma is needed or not, it just felt right. I think if I read out loud I would stop shortly after the number, which is what the comma is for after all.

However, it can be reworded as:
وُقِّعَتْ معاهدة سلام بين اليابان والصين عامّ 1978.

What do you think?

I wholly agree:
وُقِّعَتْ معاهدة سلام بين اليابان والصين عامّ 1978.

will solve this "problem" and also keep the uniformity with all the other such sentences that you translated in the current bunch ;-)

I wish the numbers could be automatically turned into arabic one day, any chance this can be turned to ١٩٧٨

I don't know Saeb but it seems that many Arabic websites and media outlets use "English numbers", Arabic Wikipedia for example uses them, so do you think the change is needed?

The thing that makes me hesitant about it is that I heard Moroccans and Algerians don't use them and might not understand them! I'm not sure but this is what I heard.

the thing is I won't push for it. I can see that they're hard to add.

I'm not the best person to talk about standards (since I don't usually follow them)...but the use of 'english numbers' are (I think) limited to the internet...you probably won't pick a national newspaper or a najeeb mahfouz novel and find them there

شخصيا أحب الأرقام العربية ^^

أنا أحبها أيضًا وأظنها تناسب الحروف العربية أكثر، لكن كما ذكرتُ فقد سمعتُ من أحدهم أن المغاربة لا يستخدمونها وبعضهم قد لا يفهمها، وإن كنتُ أشك في هذا.

أيضًا، يبدو لي أن استخدامها يسبب مشاكل في البحث، جربوا البحث عن ١ ثم البحث عن 1، وستجدون أنه لن تظهر نتائج عند البحث عن ١ أما عند البحث عن 1 فستظهر نتائج!

.أنا حزينة لأني نسيت كيف أجد الأرقام العربية من الكمبيوتر
.سوف أبحث عنها حين يكون عندي الوقت

أظنني سأبقيها كما هي حاليًّا.