一日

一日

1. (literary or dialectal) one day
2. (literary) another day in the future
3. (literary) yesterday
4. (Teochew) daytime; day

• (one day): (literary) 一旦 (yīdàn), 一天 (yītiān)
• (yesterday): 昨天 (zuótiān)
• (daytime):

一日

1. (Cantonese) as long as
   • 1999, 喜劇之王 [King of Comedy], spoken by 杜娟兒 (Karen Mok):

     聽唔聽到呀？聽唔聽到呀？一日未嗌cut，一日都要演落去，呢啲就係我成日同你哋講嘅專業。 [Cantonese, trad.]
     听唔听到呀？听唔听到呀？一日未嗌cut，一日都要演落去，呢啲就系我成日同你哋讲嘅专业。 [Cantonese, simp.]

     teng¹ m⁴ teng¹ dou^3-2 aa³? teng¹ m⁴ teng¹ dou^3-2 aa³? jat¹ jat⁶ mei⁶ aai³ kat¹, jat¹ jat⁶ dou¹ jiu³ jin² lok⁶ heoi³, ni¹ di¹ zau⁶ hai⁶ ngo⁵ seng⁴ jat⁶ tung⁴ nei⁵ dei⁶ gong² ge³ zyun¹ jip⁶.

     Did you guys hear that? As long as hasn't called “cut”, one has to continue acting. This is what I've always been telling you – professionalism.

/tuki tati/ → /t͡suitat͡ɕi/

Originally a compound of 月 (tsuki, “moon; month”) +‎ 立ち (tachi, “standing; starting, occurring”, the 連用形 (ren'yōkei, “continuative or stem form”) of verb 立つ (tatsu, “to stand up; to start, to occur”)).^[1][2][3]

• (Tokyo) ついたち (Odaka – )^[2][4]
• IPA^(key):

一日(ついたち) • (tsuitachi) 

1. the first day of the month (solar or lunar calendar)

The tsuitachi reading is the most common for the “first day of the month” sense when referring to dates.

From Middle Chinese 一日 (ʔiɪt̚ ȵiɪt̚, literally “one + day”). Compare modern Hakka reading yit-ngit.

The goon reading, so likely the initial borrowing.

• (Tokyo) いちにち (Odaka – )^[2][4]
• (Tokyo) いちにち (Heiban – )^[2]
• IPA^(key):

• When used as a modifier, the term takes pitch accent pattern 0.

一(いち)日(にち) • (ichinichi) 

1. one day, 24 hours

   一(いち)日(にち)を過(す)ごす

   ichinichi o sugosu

   to spend a day

   • 1997 December 12, Abiko, Miwa, “みかん・絵日記　おはなし⑦ [Mikan Picture Diary: Story #7]”, in みかん・絵日記 [Mikan Picture Diary], volume 2 (fiction), Tokyo: Hakusensha, page 14:

     充(じゅう)実(じつ)した一(いち)日(にち)でしたね♡お父(とう)さん

     Jūjitsushita ichinichi deshita ne ♡ otō-san

     What a fun-filled day ♡ right honey?

2. the daytime, the period from dawn until dusk
3. (figurative) a short period of time

   ローマは一(いち)日(にち)にして成(な)らず

   Rōma wa ichinichi ni shite narazu

   Rome wasn't built in a day

4. one day, someday, an unspecified day
5. the first day of the month

The ichinichi reading appears to be somewhat more common than synonymous ichijitsu below. There may be dialectal differences in usage patterns.

The tsuitachi reading is the most common for the “first day of the month” sense when referring to dates.

Ultimately from Middle Chinese 一日 (ʔiɪt̚ ȵiɪt̚, literally “one + day”). Compare modern Min Nan reading chi̍t-ji̍t.

This reading uses the goon for the first character and the kan'on for the second character, suggesting a shift in reading after the initial borrowing.

• (Tokyo) いちじつ (Odaka – )^[2]
• (Tokyo) いちじつ (Heiban – )^[2][4]
• IPA^(key):

• When used as a modifier, the term takes pitch accent pattern 0.

一(いち)日(じつ) • (ichijitsu) 

1. (literary) one day, 24 hours
2. (literary) the daytime, the period from dawn until dusk
3. (literary) (figurative) a short period of time

The synonymous ichinichi reading appears to be somewhat more common. There may be dialectal differences in usage patterns.

The tsuitachi reading is the most common for the “first day of the month” sense when referring to dates.

Compound of 一 (ichi, “one”, on'yomi, or Chinese-derived reading) +‎ 日 (hi, “day”, kun'yomi, or native-Japanese reading).^[2]

• (Tokyo) いっぴ (Atamadaka – )^[2]
• IPA^(key):

一(いっ)日(ぴ) • (ippi) ^{←いつぴ (itupi)?}

1. (rare) the first day of the month

This reading appears to be quite rare. There may be dialectal differences in usage patterns.

Compound of 一 (hito, “one”) +‎ 日 (hi, “day”).^[1][2][3] Appears in The Tale of Genji of the early 1000s CE.

• (Tokyo) ひとひ (Nakadaka – )^[2][4]
• IPA^(key):

一(ひと)日(ひ) • (hitohi) 

1. (obsolete) one day, 24 hours
2. (obsolete) the daytime, the period from dawn until dusk

/hitohi/ → /hitohe/ → /hitoe/

Shift in pronunciation from hitohi above.^[1]

• IPA^(key):

一(ひと)日(え) • (hitoe) ^{←ひとへ (fitofe)?}

1. (rare, obsolete) Synonym of 一日 (hitohi)

All senses appear to be identical as for hitohi above.